Also bear in mind that the HIP pdfs are secured so that some dishonest person cannot alter them. I am not aware of any others that offer that security.
Mine are protected they cannot be altered. I don’t use hip. I think that is why they call it a Protected Document File.
It’s actually Portable Document Format. 99% of PDF’s out there can be altered. If it doesn’t say secured in the top left then anyone with Acrobat Pro can change it. You can secure it with free programs out there then it will be a federal offense to try and edit it (violates DMCA act). Even with security enabled it’s still hackable but takes more than an off the shelf program that many people have. I believe Whisper Solutions also encrypts their PDF’s. There might be a few other programs out there now but I don’t know.