The type of handout this article refers to is the common one - namely the letter-type. And moreover this article does not adress the entire handout creation, but the simple process of making the foundation for the handout: The paper on which it is printed.
So why is this important? Well, quite simply, credibility is the key to any handout whether it is a note which serves as an adventure hook for your plot, a letter from a Baron on his deathbed or an ancient skaven map, the quality of the handouts you choose to use are proportional to their authenticity. The problem with a piece of contemporary A4 white (bleached) paper is that it is about as normal, in the Old World, as an F-22 Raptor.
You will need
How-to
First you need some music, so turn on one of the above-mentioned suggestions and make sure it is loud. Next pour some water in the bowl and add a little soy sauce. Stir a bit and add the pieces of A4 paper to the bowl. Make sure the paper is added to the mixture while the music is reaching a cresendo otherwise the color might not stick properly.
Leave the paper in the color-concoction for a few minutes depending on the desired effect and make sure that none of the pages are sticking to each other.
Grab your old newspapers and spread them out on a large table or similar surface. When the A4 papers look adequatly soaked, take them out and distribute them with no overlaps on the old newspapers.
Wait until they dry up. Apply whatever text/images are needed and start working on the edges of the paper - burn them a bit to give the impression of the wear and tear of time. If you so choose you can even just manually tear the edges to provide this effect. Congratulations, you have now created paper that embodies the spirit of the Old World.
Other considerations
The things you should consider when making handout are primarely the paper, but also the writing on the paper (duh!). We're not talking about what you write but how you write. If you are one of the few blessed individuals who have a readable handwriting and you can actually produce something which resembles calligraphy styles in Altdorf, then go jump off a cliff (we're not jealous)!! Should this not be the case some computer aided design could come in handy. A simple wordprocessor with the proper fonts installed goes a long way. Below are some websites which provides free fonts that we have found usable in our handouts.
Enjoy. Should you have any questions sacrifice a chicken and auger the entrails.