Unable to load pkcs11 module for digital signing

[manas_ag]

We have developed a pkcs11 library to interact with our key management solution. However Adobe acrobats fails to load this module citing an "Unknown Error". This module has shown to work with other softwares. 

How can we debug this further? Any system logs that we can refer to? I am not able to find any Adobe Acrobat specific documentation on how it calls the pkcs11 interface. 

Thanks, 

Manas Agarwal

[margueritek]

Acrobat requires the pkcs11 library to be signed.

[manas_ag]

Yes, we are signing the dll using signtool.

[evreny69628048]

I've experienced the same issue and after a couple of hours of research on the web, I have realized that there are two versions of the pkcs11 library on the computer: 32-bit pkcs11.dll at "C:/Windows/SysWOW64/" and 64-bit pkcs11.dll at "C:/Windows/System32/".

In my case, I was using the pkcs11 library at the 32-bit location. (I did not know this then) By 2023 Adobe has ceased support for 32-bit Acrobat, and the Acrobat on my computer silently upgraded to 64-bit by one of the routine updates. I did not even realize this update until experiencing this issue. So, my new 64-bit Acrobat stopped working with my 32-bit pkcs11.dll.

Unfortunately, Acrobat gives a generic error when you try to add the wrong-bit library to the Identities & Trusted Certificates section. So it is not easy to find what is wrong.

On the other hand, the solution is simple:

- If you have 32-bit Acrobat, use 32-bit pkcs11.dll at "C:/Windows/SysWOW64/"

- If you have 64-bit Acrobat, use 64-bit pkcs11.dll at "C:/Windows/System32/"

I hope this solution works for you.