Vit Zyka wrote (long long ago in January):

...

how is that one calculated, imagine that in the %! fields you fill in placeholders like hereshouldgosomemagiccode, then one can run a script over the pdf, calculate that magic, and replace the string; maybe this can be hooked into xpdflib Yes, I agree, postprocessing is possible. But I did not find any digest computing alg in the range of C/C++ or Perl. Also do not known links to xpdflib.

Vit Zyka

One can sign PDFs with iText (http://itextpdf.sourceforge.net/). Perhaps this helps a little bit further. I experimented a little bit, but my knowledge on PDF internas is not yet in a state that allows me to be quite creative here :-) Joachim -- Joachim Schlosser (The e-mail address is fully repliable.) http://schlosser.info