Almost all of the information contained in the PSBT is (or will be) public information. UTXOs are public, signatures are public, txids and vouts are public. The only thing that is not public are the BIP 32 derivation paths, and those aren't particularly useful to an attacker.

What "personal information" are you concerned about? What is the attack you are concerned about? If you are transmitting PSBTs over the internet, then you can employ third party tools for encryption, such as PGP. If you are concerned about a man in the middle between local machines, then you are concerned about an attacker who has gained remote access to your machines, in which case you have much bigger problems.