How can I convert a PDF to an editable Visio file?

Your drawing looks like a scanned picture actually (bitmap). It's not important if it is wrapped in PDF or whatever, the important part is that it is "just" a picture. First you'll probably need to vectorize it (so that it contains "shapes").

That is, Visio is a pure vector-graphic drawing tool. It does not have vectorization capabilities (conversion from a picture to vector graphics). You may need to use some other tool, and then convert whatever you get from that tool to Visio. You could try inkscape for example (it has "vectorization" function), or some professional tool / online service for that.

The best could be if you can get the "source" of the picture you have in PDF in some vector format (SVG for example).

In my opinion, what you are trying to do is next to impossible. it could be easier just to draw the map from scratch.

Visio can't work directly with PDF files. Either get a PDF file editor, or convert the PDF into DXF format (there are free converters available for that job), then import the DXF file into Visio.