This post will focus on the Windows operating system, but similar issues apply to Linux, Mac OS, and the operating systems for IBM mainframes. When we think of the type of documents that are likely to be notarized, PDF immediately comes to mind, but there are other file formats that are designed to accommodate digital signatures, and there could be use cases for notarizing in these formats.
Perhaps the most obvious PDF alternative would be the Microsoft Office formats, including Word and Excel. These programs have built-in electronic signature support, and many people have access to these programs. Access to the program needed to create PDFs with digital signatures, Adobe Acrobat, is much more limited. There are freeware alternatives to Microsoft Office, such as libreoffice/ although their eSignatures are not compatible with Microsoft Office.
A less common format, but potentially important in the real estate world, is Autocad (.dwg). This is a popular format for technical drawings, including land surveys.
If a notary obtains a digital certificate from a general-purpose certificate authority, such as IdenTrust the notary could use it to notarize any of the files described above. But if the notary uses one of the online platforms specifically intended for eNotarizations, such as DocVerify, the result will always be a PDF. Obviously, such formats won't be useful for some situations. For example, when viewing an AutoCad drawing, one can easily zoom in and out, measure distances, and turn layers on and off; those actions would be impossible or difficult with a PDF.