I need to change the value of a field in an existing PDF file.

I am using PdfReader, PdfStamper and AcroFields and that's working fine. But, in doing so, it is required to create a new PDF and I would like the change to be reflected in the existing PDF itself. If I am setting the destination filename to be the same as the original filename, then my application fails.

Posted on StackOverflow on Apr 18, 2013 by tk2013

You can't read a file and write to it simultaneously. Think of how Microsoft Word works: you can't open a Word document and write directly to it. Word always creates a temporary file, writes the changes to it, then replaces the original file with it, and then throws away the temporary file.

You can do that this way:

  • read the original file with PdfReader;

  • create a PdfWriter instance for the resulting PDF;

  • create a PdfDocument to manipulate the original file

This example is written using iText 7:

PdfReader reader = new PdfReader(src);
PdfWriter writer = new PdfWriter(dest);
PdfDocument pdfDoc = new PdfDocument(reader, writer);
//manipulate pdf…

Click How to update a PDF without creating a new PDF? if you want to see how to answer this question in iText 5.