Where can I get a Manual for OS X Mavericks 10.9.5?

Perhaps look online or in second hand/used bookstore

for a manual from Missing Manuals by David Pogue..

Some online versions may exist; or may appear to be

yet might also be bait. (scans by google might be OK)

https://duckduckgo.com/?t=ftsa&q=user+manuals+pogue+missing+manual+os+x+10.9.5&ia=web

In past years, these were available at much less cost than

new; within few years of publication, at charity thrift stores.

[I've a few Missing Manuals, but not by Pogue; they're OK.]

The google books seem to be limited to previews, not complete.

OS X Mavericks: The Missing Manual - David Pogue - Google Books

https://books.google.com/books/about/OS_X_Mavericks_The_Missing_Manual.html?id=-7hdAgAAQBAJ

My Late 2012 Mac mini 'server edition' included Mavericks.

Seems it had OK version of OS X Help, but not super good.

Just an FYI, unless you have very specific software only made for Mavericks, it is highly recommended you go to El Capitan. Both OSes have the same minimum hardware requirements. You can get the El Capitan installer from:

How to download and install macOS - Apple Support