Let me grab my crystal ball and guess that by "DRM" you mean detecting whether the document has been altered or not, given that keeping people from copying a document is impossible. In that case, you don't need a Windows program. LibreOffice, which does either everything MS Office can do or close to it, can sign documents for you. LibreOffice runs natively on Linux, Mac, and Windows, that is, without WINE or VirtualBox or any compatibility aids. It uses asymmetrical encryption (that's where one key decrypts and one key encrypts) so that only you, the sole bearer of the secret private key, can create a signature for a document that when someone takes the public key, which you bundle with the document and release to a certificate authority and is mathmatically related to the private key, and uses that with a hash of the document, the signature is computed. If it matches the signature bundled with the document, then it's an original. If not, then the document has been altered. One could verify that that really is your public key by going to the certificate authority with whom you registered that public key with your name. I think the way it works is a hash is made of the document, then you encrypt that hash with your private key and bundle the encrypted hash with the document. You also bundle in the public key and your name. Then someone else who obtains the document can calculate the hash, decrypt the encrypted hash with the supplied public key, and see if the hashes match. If anyone alters the document, the hashes won't match. If someone replaces the encrypted hash and public key so that the hashes will match for the altered document, by going to the certificate authority one could see that that public key is not registered with who the author is supposed to be. Cheers, Jake
