I've used various methods (mentioned elsewhere on this site) to create PDFs, using a printer driver or converting from PostScript, etc. The common problem is that if I open any of the output files in the newer versions of Adobe Reader, there's an option to "Place Signature" but it's greyed out, or gives an error message that the feature has been disabled for this document. As far as I can tell, there's an option set somewhere in the document metadata that tells Reader "allow the user to sign this document", or don't. None of the free/open source tools that have been been linked to in other SU posts have had this listed as an option (though to be fair I haven't actually downloaded and tried all of them).

Is there a tool that does this? Can I just poke a bit with a hex editor somewhere to turn on this functionality? I can sometimes get access to Acrobat Professional to turn on this option, but doing it for every desired case would be more work than I care to do. The current workaround for single-page documents is:

1. Print the document to PDF (possibly via postscript)
2. Open a single-page blank PDF with the "signable" bit turned on in Reader
3. create a custom "stamp" using the Reader markup tools, by importing the printed-to document
4. "stamp" an image of the printed document on the blank page, hoping to get it centered about right
5. place a signature over the document-but-not-really you just stamped

This obviously does not scale well at all. It would be much better if I could:

1. Print the document to PDF
2. Drag the document to a simple shortcut / tool / whatever
3. Open the document in Reader
4. Place a signature in the document

ETA: Sorry, maybe I should have been clearer -- I'm talking about the certificate-based digital signing available in Adobe Reader, not adding a virtual ink signature. Also, any solution really would have to be available offline.