How to Digitally Sign a PDF Document?

(For the latest PDF files Merger Software please have a look at the top of the left margin, inside the red box.) Now this basic signature manager is ready in Codes For Us PDF Merging utility, R6 series (here). It is yet far from being complete. You notice that to use it one needs a PFX (PKCS#12) to have ready somewhere either self-signed or CA signed. I have a humble tweak GUI to create that PFX at home using self signature, available in download area. My 'uber-geek' friend Grant Hardy (who is a microwave engineer and has implemented Messiah's Calendar [he sleeps on a Smith's Chart at nights]) has promised to give a hand to meet our promised milestone around the Christmas, for further features to be accompanied (e.g., a password remover is ready now done by him, a password unlocker he is also interested as a matter of algorithm tests, not by using a brute force). With this Signature Manager one cannot put her seal emblem on the digital signature. It is just a standard digital signature of PDF documents as it is defined. The Water-mark utility provided by Codes For Us might meet that demand, if one is interested. But people are interested to have emblem next, or as under-layer to their digital signature, too. Hence, I try to add that feature, later to the manager (04/Jan/11: Now the feature is added)). I hope you enjoy this version for now.
Update 04/January/11: Now notarize PDF with external timestamp, seal emblem under-layer, and few other features are included. Codes For Us PDF Merging utility, 01/March/11, beta_6_7 (here).
Update 05/March/11: Now with a visual help page (here).