Is it possible to mark a string in pdf document?

Question

I was wondering if it was possible to mark strings in pdf with different color or underline them while looping through the pdf document ?

Answer 1

It's possible on creating a document. Just use different chunks to set the style. Here's an example:

Document document = new Document();
PdfWriter.getInstance(document, outputStream);
document.open();
document.add(new Chunk("This word is "));

Chunk underlined = new Chunk("underlined");
underlined.setUnderline(1.0f, -1.0f); //We can customize thickness and position of underline
document.add(underlined);

document.add(new Chunk(". And this phrase has "));

Chunk background = new Chunk("yellow background.");
background.setBackground(BaseColor.YELLOW);
document.add(background);

document.add(Chunk.NEWLINE);
document.close();

However, it's almost impossible to edit an existing PDF document. The author of iText writes in his book:

In a PDF document, every character or glyph on a PDF page has its fixed position, regardless of the application that’s used to view the document. This is an advantage, but it also comes with a disadvantage. Suppose you want to replace the word “edit” with the word “manipulate” in a sentence, you’d have to reflow the text. You’d have to reposition all the characters that follow that word. Maybe you’d even have to move a portion of the text to the next page. That’s not trivial, if not impossible.

If you want to “edit” a PDF, it’s advised that you change the original source of the document and remake the PDF.

Answer 2

Aspose.PDF APIs support to create new PDF document and manipulate existing PDF documents without Adobe Acrobat dependency. You can search and add Highlight Annotation to mark PDF text.

REST API Solution using Aspose.PDF Cloud SDK for Java:

// For complete examples and data files, please go to https://github.com/aspose-pdf-cloud/aspose-pdf-cloud-java
String name = "02_pages.pdf";
String folder="Temp";
String remotePath=folder+"/"+name;
// File to upload
File file = new File("C:/Temp/"+name);
// Storage name is default storage
String storage = null;

// Get App Key and App SID from https://dashboard.aspose.cloud/
PdfApi pdfApi = new PdfApi("xxxxxxxxxxxxxxxxxxxx", "xxxxx-xxxx-xxxx-xxxx-xxxxxxxxx");
//Upload file to cloud storage
pdfApi.uploadFile(remotePath,file,storage);
        
//Text Position
Rectangle rect = new Rectangle().LLX(259.27580539703365).LLY(743.4707997894287).URX(332.26148873138425).URY(765.5148007965088);

List<AnnotationFlags> flags = new ArrayList<>();
flags.add(AnnotationFlags.DEFAULT); 

HighlightAnnotation annotation = new HighlightAnnotation();
annotation.setName("Name Updated");
annotation.rect(rect);
annotation.setFlags(flags);
annotation.setHorizontalAlignment(HorizontalAlignment.CENTER);
annotation.setRichText("Rich Text Updated");
annotation.setSubject("Subj Updated");
annotation.setPageIndex(1);
annotation.setZindex(1);
annotation.setTitle("Title Updated");       
annotation.setModified("02/02/2018 00:00:00.000 AM");


List<HighlightAnnotation> annotations = new ArrayList<>();
annotations.add(annotation);
//Add Highlight Annotation to the PDF document
AsposeResponse response = pdfApi.postPageHighlightAnnotations(name,1, annotations, storage, folder);

//Download annotated PDF file from Cloud Storage
File downloadResponse = pdfApi.downloadFile(remotePath, null, null);
File dest = new File("C:/Temp/HighlightAnnotation.pdf");
Files.copy(downloadResponse.toPath(), dest.toPath(), java.nio.file.StandardCopyOption.REPLACE_EXISTING);
System.out.println("Completed......");

On-Premise Solution using Aspose.PDF for Java:

// For complete examples and data files, please go to https://github.com/aspose-pdf/Aspose.Pdf-for-Java
// Instantiate Document object
Document document = new Document("C:/Temp/Test.pdf");
// Create TextFragment Absorber instance to search particular text fragment
TextFragmentAbsorber textFragmentAbsorber = new TextFragmentAbsorber("Estoque");
// Iterate through pages of PDF document
for (int i = 1; i <= document.getPages().size(); i++) {
    // Get first page of PDF document
    Page page = document.getPages().get_Item(i);
    page.accept(textFragmentAbsorber);
}

// Create a collection of Absorbed text
TextFragmentCollection textFragmentCollection = textFragmentAbsorber.getTextFragments();

// Iterate on above collection
for (int j = 1; j <= textFragmentCollection.size(); j++) {
    TextFragment textFragment = textFragmentCollection.get_Item(j);

    // Get rectangular dimensions of TextFragment object
    Rectangle rect = new Rectangle((float) textFragment.getPosition().getXIndent(), (float) textFragment.getPosition().getYIndent(), (float) textFragment.getPosition().getXIndent() + (float) textFragment.getRectangle().getWidth(), (float) textFragment.getPosition().getYIndent() + (float) textFragment.getRectangle().getHeight());

    // Instantiate HighLight Annotation instance
    HighlightAnnotation highLight = new HighlightAnnotation(textFragment.getPage(), rect);
    // Set opacity for annotation
    highLight.setOpacity(.80);  
    // Set the color of annotation
    highLight.setColor(Color.getYellow());
    // Add annotation to annotations collection of TextFragment
    textFragment.getPage().getAnnotations().add(highLight);
}
// Save updated document
document.save("C:/Temp/HighLight.pdf");

P.S: I work as support/evangelist developer at Aspose.