Yes. Yes it absolutely is!!!
At least, the old Win32 PDBs are. The new portable PDBs introduced with .NET Core are a much cleaner design and are much easier to work with.
The main problem with the old PDBs is that they were clearly only ever intended to be an internal format. It's generally best to interface with the files using the old COM based service calls (i.e. ISymUnmanagedWriter3) rather than interact with them yourself. However, if you're up for the challenge, the Mono.Cecil project has a managed PDB reader that can read all the essentials by leveraging the old CCI code.
Generally, I would recommend against investing time in learning this file format unless you have a good reason to do so. It wouldn't surprise me if MS decided to deprecate the format entirely and move everything to portable PDBs. You can imagine that they don't enjoy interacting with that old stuff any more than we do.