in short: You can use any app you feel comfortable with!
but there may be requirements by the company you work for?
because other people may want to view and maintain those files!
I can give no recommendation for apps used, more likely WHAT documents
of course the app used is different per use of the document
there are different types of files that are helpful
- network diagrams (both Layer-2 and Layer-3)
can be created in many ways, Viso, PPT, CAD, even in MS-paint (but paint is not easy when making changes)
Also Cisco packet tracer can be a use full tool to design and document (and even test) your network design!
Cisco provides PowerPoint symbols, Visio stencils, CAD-files , etc
- inventory lists (spreadsheet / sharepoint list / database)
- documents (PDF, Word) to describe the requirements of design, and arguments for the design chosen
- configuration files
- 19-inch rack layout
- maps of the building -> where is equipment placed
- list of contacts at the location, and for access (like keys needed etc)
