I have no idea how secure the protection is in WordPerfect suffice to say that the “Original password protection” is useless and can be cracked in no time. According to their website they now provide “Enhanced password protection” but it doesn’t say what algorithm it uses and it doesn’t refer to it as “encryption”. I would conclude that it’s insecure and you should probably use AxCrypt.
Microsoft Office properly encrypts files in their new versions and when used with a secure password it cannot be broken. The benefit of using Microsoft’s encryption is that it’s device agnostic, you can open your Office files in iOS, Android, Windows or Windows Phone without AxCrypt.
At the moment AxCrypt doesn’t allow you to edit your files on a mobile device so you should bear this in mind however a quick search shows that WordPerfect doesn’t have mobile apps so AxCrypt looks like a good fit.
The only people who use WordPerfect tend to be lawyers and I’m assuming you’re not one because of your question about HIPAA. You can search Google for a fuller explanation but it’s not software that needs to be compliant, it’s your practices and using password protection (WordPerfect) instead of encryption (AxCrypt) is not HIPAA compliant. I don’t think they even grant certificates of HIPAA compliance!