Using pdflib on a scanned document

Question

I got a scanned document in pdf and noticed in the file>properties that the "pdf producer" is pdflib 6.0.3

Questions:

1. why and how was pdflib used to produce this pdf? It was supposed to be a scanned document.
2. why "created" timestamp is later than "modified" timestamp?
3. could somehow the scanned document have been edited after it was scanned by pdflib?
4. is there a way to see all changes done (if any) ?

My concern is that the scanned document has been edited when it shouldn't have been. Something looks weird.

Thanks, Spike

I tried looking up pdflib tutorial but couldn't figure it out

Answer 1

why and how was pdflib used to produce this pdf? It was supposed to be a scanned document.

in general, a scanner provides a raster image. To convert this into a PDF, you can do this with appropriate tools. And here PDFlib seems to have been used to place a raster image (with perhaps additional (meta) information) into a PDF.

why "created" timestamp is later than "modified" timestamp?

PDFlib writes only the modified entry to a PDF. In this case another PDF software seems to have modified the PDF file.

could somehow the scanned document have been edited after it was scanned by pdflib?

technically this is possible. However, in most cases only the metadata (like the Document Information fields) has been adjusted. That the raster images contained in the PDF have been changed is rather unlikely.

is there a way to see all changes done (if any) ?

There is usually no way to track that. Theoretically there is a possibility to save the changes in XMP, but this is not used by any producer.

the only way to detect a change in PDFs is when a PDF file is signed with a digital signature. Then the signature becomes invalid as soon as even 1 bit changes in the PDF file. This could ensure authenticity. But this technique is not widely used.

Hope this short answer helps.