combine_pdf gem : PDF is Encrypted! Attempting to decrypt - not yet fully supported

Question

Trying to merge PDF file

I'm using version (1.0.16) and tried (1.0.21) also, but still getting this error PDF is Encrypted! Attempting to decrypt - not yet fully supported.

I'm able to open the file in preview without password.

I see this issue, which is already discussed issue#66 and closed but still getting error, any help here?

https://github.com/boazsegev/combine_pdf/issues/196