I guess my question is rather simple. All I found in my research were threads with very short answers sounding like "DAT SO EZ LUK HEER NAP: link".. I tried those links and they were all 404.. So I'm exposing myself to another public execution and will try this thread a millionth time.
I'm working with PDFBox 2.0.17 and I am trying to sign a PDF-File with an already existing pfx-certificate. Thats pretty much everything. I got some pretty disgusting solutions myself with printing the file via pdf-Creator and stuff, but there must be a smoother, nicer solution.
I'd be pretty thankful for every non-404-Link and will accept any kind of public humiliation.
Best regards, YXCD
P.S.: Of course I found solutions like PDFone and other providers. But I'm trying to do this without getting myself bankrupt ..
Okay, to sum this up..
My experience here is that PDFBox has some very precise dependencies which will throw Exceptions the moment they are slightly out of version. I fixed every problem by first of all reloading the entire PDFBox-Files and then downloading every dependencies the exact version as listed in the PDFBox Version. Using newer versions will throw exceptions.
At the end I took the CreateSignature-Example and rewrote it for my needs. Then it all worked perfectly and smoothly.
Thanks to @mkl and @TilmanHausherr for your comments and giving me the right guidelines.