I have received encrypted PDF which contains several string objects but not all of them are encrypted.
I am not sure whether it is or it is not compliant with pdf reference.
But I have created fix so pdfbox can handle this.
If string contains only chars between 32-127 then decryption is not necessary (I know, this is not true in 100% of cases but I think it is swallowable)
Some strings are encrypted:
Some are not: