you can decrypt an encrypted file and have it display on terminal with gpg -d and it just treats it as any other ciphertext, the output will not be very helpful in 99.99% of cases though, your shell doesn't know what to do with a pdf file it just displays the raw bytes. To get it so that you can view it with a pdf reader, I don't know of a solution other than to save the output as a .pdf on the disk and then open it with the pdf reader. I tried to pipe the decrypted output to a reader from my terminal in the following way and it failed to work: gpg -d test.pdf.gpg | evince a solution would therefor be to put the ciphertext in a virtual machine, then decrypt it and save it as a .pdf file, then open that file. You can do all of this from memory with a virtual machine, but without a virtual machine I don't know how else you would load the plaintext as a .pdf file with your reader without having to write it to the HD, since the file is saved as a .pdf only in the virtual machine which you can configure to be entirely in the hosts RAM.