New PDF Document API: Find, Edit, Redact or Remove Text

• 7 minutes to read

The new PDF Document API allows you to find text in PDF documents and edit the search results. The following actions are available:

• Find text in a PDF document
• Format search results (change font, color, and so on)
• Replace search results with new text
• Remove or redact search results

Run Demo: Find and Highlight Text

Basic Concept: Search Result Structure

Call the PdfDocument.FindText method to start a search. You can specify the page range and search settings (whole words, case sensitivity, and so on).

The FindText method returns a list of TextSearchInfo objects that contain search results. Each object contains results found on a single page. A TextSearchInfo object returns two lists:

Matches

Use this list to obtain search result coordinates on page (rectangles). These rectangles can be used to redact or draw over search results.

Groups

Use this list to format search results. This list allows you to access text fragments in the document.

Find Text

The following code snippet searches for the word “DevExpress” on the first three pages of a PDF document:

C#

using DevExpress.Docs.Pdf;
using System.Collections.Generic;
using System.IO;

using (FileStream fileStream =
    File.OpenRead(@"Document.pdf"))
{
    using (PdfDocument pdfDocument = new PdfDocument(fileStream))
    {
        // Search for text in the first three pages.
        IEnumerable<TextSearchInfo> results =
            pdfDocument.FindText("DevExpress",
                new TextSearchOptions(true, true), 0, 2);

        foreach (TextSearchInfo searchResult in results)
        {
            // Process search results.
        }

        pdfDocument.Save(
            File.OpenWrite(
                @"Document_upd.pdf"));
    }
}

VB.NET

Imports DevExpress.Docs.Pdf
Imports System.Collections.Generic
Imports System.IO

Using fileStream As FileStream = _
        File.OpenRead("Document.pdf")
    Using pdfDocument As New PdfDocument(fileStream)
        ' Search for text in the first three pages.
        Dim searchResults As IEnumerable(Of TextSearchInfo) = _
            pdfDocument.FindText("DevExpress", _
                New TextSearchOptions(True, True), 0, 2)

        For Each searchResult As TextSearchInfo _
                In searchResults
            ' Process search results.
        Next

        pdfDocument.Save( _
            File.OpenWrite( _
                "Document_upd.pdf"))
    End Using
End Using

Format Search Results

Use the TextSearchInfo.Groups property to get the collection of text groups that match the search pattern. Each TextMatchGroup object contains a Fragment property that returns a TextFragment object. Use the fragment’s properties to change text formatting.

The following code snippet changes the font color of matching text fragments:

C#

using DevExpress.Docs.Pdf;
using System.Collections.Generic;
using System.Drawing;
using System.IO;

using (FileStream fileStream =
    File.OpenRead(@"Document.pdf"))
{
    using (PdfDocument pdfDocument =
        new PdfDocument(fileStream))
    {
        IEnumerable<TextSearchInfo> results =
            pdfDocument.FindText("DevExpress",
                new TextSearchOptions(true, true), 0, 2);

        foreach (TextSearchInfo searchResult in results)
        {
            foreach (var group in searchResult.Groups)
            {
                // Split the fragment into matched parts.
                var newFragments = group.Fragment
                    .Split(group,
                        out TextFragment[] matched,
                        out TextFragment[] notMatched);

                // Apply formatting to matched fragments.
                foreach (var matchedFragment in matched)
                {
                    matchedFragment.Font = 
                        new TextFont("Arial", TextFontStyle.Bold);
                    matchedFragment.ForegroundFill = new SolidFill(PdfColor.Red);
                }

                pdfDocument.Pages[searchResult.PageIndex]
                    .Fragments.Replace(
                        group.Fragment, newFragments);
            }
        }

        pdfDocument.Save(new FileStream(
            "Result.pdf", FileMode.Create,
            FileAccess.Write));
    }
}

VB.NET

Imports DevExpress.Docs.Pdf
Imports System.Collections.Generic
Imports System.Drawing
Imports System.IO

Using fileStream As FileStream = _
        File.OpenRead("Document.pdf")
    Using pdfDocument As New PdfDocument(fileStream)
        Dim searchResults As IEnumerable(Of TextSearchInfo) = _
            pdfDocument.FindText("DevExpress", _
                New TextSearchOptions(True, True), 0, 2)

        For Each searchResult As TextSearchInfo _
                In searchResults
            For Each group In searchResult.Groups
                ' Split the fragment into matched parts.
                Dim matched As TextFragment() = Nothing
                Dim notMatched As TextFragment() = Nothing
                Dim newFragments As TextFragment() = _
                    group.Fragment.Split( _
                        group, matched, notMatched)

                ' Apply formatting to matched fragments.
                For Each matchedFragment In matched
                    matchedFragment.Font = New TextFont("Arial", TextFontStyle.Bold)
                    matchedFragment.ForegroundFill = New SolidFill(PdfColor.Red)
                Next

                pdfDocument.Pages(searchResult.PageIndex) _
                    .Fragments.Replace( _
                        group.Fragment, newFragments)
            Next
        Next

        pdfDocument.Save(New FileStream( _
            "Result.pdf", FileMode.Create, _
            FileAccess.Write))
    End Using
End Using

Replace Text

Use the TextSearchInfo.Groups property to get the collection of text groups that match the search pattern. Call the TextFragment.Split(TextMatchGroup, TextFragment[], TextFragment[]) method to split the original text fragment into matched and unmatched parts, change the text of the matched fragments, and call the FragmentCollection.Replace method to replace the original fragment with the resulting fragments on the page.

The following code snippet replaces all “Lorem Ipsum” occurrences with “DevExpress Rocks!”:

C#

using DevExpress.Docs.Pdf;
using System.Collections.Generic;
using System.IO;

using (PdfDocument pdfDocument = new PdfDocument(
    new FileStream(@"Document.pdf", FileMode.OpenOrCreate, FileAccess.ReadWrite)))
{
    IEnumerable<TextSearchInfo> searchResults =
        pdfDocument.FindText("Lorem Ipsum", new TextSearchOptions(false, true));

    foreach (TextSearchInfo result in searchResults) {
        foreach (TextMatchGroup group in result.Groups) {
            // Split the fragment into matched and unmatched parts.
            TextFragment[] newFragments = group.Fragment.Split(
                group, out TextFragment[] matched, out TextFragment[] notMatched);

            // Replace the text of the matched fragments.
            foreach (TextFragment matchedFragment in matched) {
                matchedFragment.Text = "DevExpress Rocks!";
            }

            pdfDocument.Pages[result.PageIndex].Fragments.Replace(group.Fragment, newFragments);
        }
    }
    pdfDocument.Save(new FileStream("Result.pdf", FileMode.Create, FileAccess.Write));
}

VB.NET

Imports DevExpress.Docs.Pdf
Imports System.Collections.Generic
Imports System.IO

Using pdfDocument As New PdfDocument(
    New FileStream("Document.pdf", FileMode.OpenOrCreate, FileAccess.ReadWrite))

    Dim searchResults As IEnumerable(Of TextSearchInfo) =
        pdfDocument.FindText("Lorem Ipsum", New TextSearchOptions(False, True))

    For Each result As TextSearchInfo In searchResults
        For Each group As TextMatchGroup In result.Groups
            ' Split the fragment into matched and unmatched parts.
            Dim matched As TextFragment()
            Dim notMatched As TextFragment()
            Dim newFragments As TextFragment() = group.Fragment.Split(group, matched, notMatched)

            ' Replace the text of the matched fragments.
            For Each matchedFragment As TextFragment In matched
                matchedFragment.Text = "DevExpress Rocks!"
            Next

            pdfDocument.Pages(result.PageIndex).Fragments.Replace(group.Fragment, newFragments)
        Next
    Next
    pdfDocument.Save(New FileStream("Result.pdf", FileMode.Create, FileAccess.Write))
End Using

Redact Search Results

Use redaction annotations to redact search results. Create a RedactionAnnotation object and specify the text fragment’s rectangle as the annotation’s bounds. Call the PdfDocument.ApplyRedaction method to apply redaction annotations to a PDF document. Once the redaction annotation is applied, it cannot be retrieved, edited, or removed.

You can add call the Page.Annotations.Add method to add a redaction without applying it.

The following code snippet redacts search results:

C#

using DevExpress.Docs.Pdf;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Linq;

// Load the PDF document.
using (PdfDocument pdfDocument = new PdfDocument(
    new FileStream(@"Document.pdf",
        FileMode.OpenOrCreate, FileAccess.ReadWrite)))
{
    // Search for text in the first three pages.
    IEnumerable<TextSearchInfo> results =
        pdfDocument.FindText("DevExpress",
            new TextSearchOptions(true, true), 0, 2);

    // Iterate through search results.
    foreach(var result in searchResults) {
        List<RedactionAnnotation> annotations = new List<RedactionAnnotation>();
        foreach(var match in result.Matches) {
            // Get rectangles of matched text fragments.
            var rectangles = match.MatchFragments
                .Select(f => f.Rectangle).ToArray();
            // Create a redaction annotation with specified settings.
            var annotation = new RedactionAnnotation(RectangleF.Empty) {
                Geometry = new RedactionGeometry(rectangles),
                FillColor  = PdfColor.Black,
                Color  = PdfColor.Red,
                OverlayText = string.IsNullOrEmpty(redactionText) ? null : redactionText,
                CreationDate = DateTime.UtcNow,
                TextJustification = TextJustification.LeftJustified,
                RepeatText = true,
                TextAppearance = new TextAppearance() {
                    FontSize = 0,
                    Fill = SolidFill.White,
                }};
            annotations.Add(annotation);
        }
        // Apply redaction or add annotations to the page.
        if(applyRedaction)
            doc.ApplyRedaction(result.PageIndex, annotations.ToArray());
        else
            foreach(var ann in annotations)
                doc.Pages[result.PageIndex].Annotations.Add(ann);
    }

// Save the result document.
using (FileStream fileStream = new FileStream(
        "Result.pdf", FileMode.Create,
        FileAccess.Write)) {
    pdfDocument.Save(fileStream);
}

VB.NET

Imports DevExpress.Docs.Pdf
Imports System.Collections.Generic
Imports System.Drawing
Imports System.IO

' Load the PDF document.
Using pdfDocument As New PdfDocument( _
        New FileStream("C:\Test Documents\Document.pdf", _
            FileMode.OpenOrCreate, FileAccess.ReadWrite))
    ' Search for text in the first three pages.
    Dim searchResults As IEnumerable(Of TextSearchInfo) = _
        pdfDocument.FindText("DevExpress", _
            New TextSearchOptions(True, True), 0, 2)

    ' Iterate through search results.
    For Each result In searchResults
        Dim annotations As New List(Of RedactionAnnotation)()
        For Each match In result.Matches
            ' Get rectangles of matched text fragments.
            Dim rectangles = match.MatchFragments _
                .Select(Function(f) f.Rectangle).ToArray()
            ' Create a redaction annotation with specified settings.
            Dim annotation As New RedactionAnnotation(RectangleF.Empty) With {
                .Geometry = New RedactionGeometry(rectangles),
                .FillColor = PdfColor.Black,
                .Color = PdfColor.Red,
                .OverlayText = If(String.IsNullOrEmpty(redactionText), Nothing, redactionText),
                .CreationDate = DateTime.UtcNow,
                .TextJustification = TextJustification.LeftJustified,
                .RepeatText = True,
                .TextAppearance = New TextAppearance() With {
                    .FontSize = 0,
                    .Fill = SolidFill.White
                }
            }
            annotations.Add(annotation)
        Next
        ' Apply redaction or add annotations to the page.
        If applyRedaction Then
            pdfDocument.ApplyRedaction(result.PageIndex, annotations.ToArray())
        Else
            For Each ann In annotations
                pdfDocument.Pages(result.PageIndex).Annotations.Add(ann)
            Next
        End If
    Next

    ' Save the result document.
    Using fileStream As New FileStream( _
            "Result.pdf", FileMode.Create, _
            FileAccess.Write)
        pdfDocument.Save(fileStream)
    End Using

Remove Found Text

The PdfDocument.RemoveText method accepts search results or a string value.

The following code snippet removes the word “DevExpress” from the document:

C#

using DevExpress.Docs.Pdf;
using System.Collections.Generic;
using System.IO;

using (PdfDocument pdfDocument = new PdfDocument(
    new FileStream(@"Document.pdf",
        FileMode.OpenOrCreate, FileAccess.ReadWrite)))
{
    IEnumerable<TextSearchInfo> results =
        pdfDocument.FindText("DevExpress",
            new TextSearchOptions(true, true), 0, 2);

    // Remove the found text.
    pdfDocument.RemoveText(results);

    pdfDocument.Save(new FileStream(
        @"C:\Test Documents\Result.pdf",
        FileMode.Create, FileAccess.Write));
}

VB.NET

Imports DevExpress.Docs.Pdf
Imports System.Collections.Generic
Imports System.IO

Using pdfDocument As New PdfDocument( _
        New FileStream("C:\Test Documents\Document.pdf", _
            FileMode.OpenOrCreate, FileAccess.ReadWrite))
    Dim searchResults As IEnumerable(Of TextSearchInfo) = _
        pdfDocument.FindText("DevExpress", _
            New TextSearchOptions(True, True), 0, 2)

    ' Remove the found text.
    pdfDocument.RemoveText(searchResults)

    pdfDocument.Save(New FileStream( _
        "C:\Test Documents\Result.pdf", _
        FileMode.Create, FileAccess.Write))
End Using