Hi Joanna,
We were stuck with version1.3 since this was the DLL utilized by the vendor's application. I discovered that it uses 128-bit RC4 encription, a routine that has been rendered insecure. Sorry I can't provide the link where I discovered the encryption method, like you I had a rough go finding this out, and apparently didn't document the location I discovered this at.
REF:
https://en.wikipedia.org/wiki/RC4Version 1.3 also has issues merging PDF files in Version 6 or later.
REF:
http://forum.pdfsharp.net/viewtopic.php ... ef+streamsThese were show-stoppers for us since we handle HIPAA information. I did some research and found a nice little cheap (but not free) application called Coherent PDF. We just needed to be able to call the DLL, for Merging and Encryption, and it works like a charm. Encryption is 256 AES, the same encryption utilized by the CDC, and exceeding HIPAA requirements.
You might want to check it out. Here is the URL for the website:
https://www.coherentpdf.com/ Server license was less than $500.
Best of luck!