Aged documents:
Use parchment paper. It has a nice sturdiness to it and is appropriate for old-looking documents.
Use india ink (preferably from a bottle) and a calligraphy pen or fountain pen if you have one.
Don't mind a few drips and smears. Few people besides upper classmen, scholars and monks were overly concerned with style. Maps should also be drawn out with the pen.
You can carefully burn the edge of parchment with a lighter. I wouldn't recommend an oven, but perhaps a stove would be okay. Keep a bucket of water handy just in case!
Soaking and drying have already been mentioned. In addition to sun drying, you can always use a clothes iron as well.
Wax seals are an option if you're willing to spend the money. And a touch of perfume if it's a love letter, or fake blood stains if somebody was killed over it are a nice touch.
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As for maps:
I only take what I can print out on paper, so I don't do a lot of computer editing of maps. Maps are one thing I still prefer to do on paper. I wouldn't call it old-school, but it just takes too long to edit things on a computer and it doesn't take that much longer by hand.
True "final" quality maps are more easily decorated or flourished by hand as well. You just don't get much embellishment from software programs.
I use vellum (it's a professional tracing paper) to draw out the different layers of a complex. It is especially useful if you have a more vertical dungeon rather than a flat, level one.
For anybody looking for a mapping tutorial, the very end of the Dungeoneer's Survival Guide has a very good one for beginners. I would highly recommend it if you have the time and interest to make more professional looking maps.
Vellum is also very handy to quickly produce an accurate player's map if needed (usually any map the PC's buy from a store vendor are of accurate quality, otherwise I'll freehand or guestimate). Or you can alter premade maps easily with vellum as well.