Where to find trail maps?

I would start with the Austrian Tourist office online, but then follow up at the tourist office in Salzburg in person, where they probably sell good maps and could offer advice. http://www.austria.info/uk/nature-recreation or see also http://maps.kompass.at/.

Most book stores will carry hiking maps and guide books for the local region. The terms in German are Wandelkarte and Wandelführer, respectively.

I have used the Kompass Wanderkarten in the past and I liked them. Someone gave the website above.

Khttp://www.untersberg-drache.de/wandern-und-bergsteigen/wanderkarten/

Deutscher Alpenverein:

Very useful and detailed map for walking around the Unterberg.

Wanderkarte Untersburg:

.. With various panoramic views and suggestions for tours incl relief
map (with German and English description) Other topics include:
attractions, location descriptions, opening times, public transport,
information on accommodation, shelter, Attractions, inns and culture.

http://www.groedig.net/hiking-salzburg

The mountain hiking school, Salzburg Alpin, is a helpful partner for
hikers, and the Tourist Information Center in Grödig will gladly
assist with maps and valuable suggestions.

For planning:

Wanderwegbeschreibung Grossgmain und Bayerisch Gmain
http://www.grossgmain.info/medien/wanderkarte.pdf