Signature box is invalid when signing PDF

[ridgey-dev]

Input PDF:
input.pdf

Undesired result:
output.pdf

When signing the document twice (so user can see multiple signature boxes on different pages) the result is that the only the last created signature box is valid. The first one has message "Document has been altered or corrupted since it was signed.".

Note that the input.pdf contains unsigned signature boxes, and it has been made using phpunite.

Code:

$document = PDFDoc::from_string($content);
$document->sign_document($certfile);
$content = $document->to_pdf_file_s();

$document = PDFDoc::from_string($content);
$document->sign_document($certfile);
$content = $document->to_pdf_file_s();

file_put_contents('output.pdf', $content);

[ridgey-dev]

Is there already some progress on this that could be shared?

[angeljqv]

Feel free to make a PR with the fix

[ridgey-dev]

I don't have a fix for it. I was kinda hoping a contributor could look into it to have some insights why it's working like this for this document.

The workaround for me right now is that I create a new PDF by loading the file into QPDF. Signing the output of that won't generate an error. This is of course not very helpful for a fix in this package, but maybe it could help finding the root problem.