There are a number of other sites which have collections of downloadable paper props. You don’t necessarily need to search for theatre props; there are large communities of replica prop makers and role-playing game prop makers with all manner of documents available online.
The H.P. Lovecraft Historical Society has a number of replica paper props from the early twentieth century, such as telegrams, drivers licenses, and library cards. They also have a nice section on making paper props.
P.I. Vintage has a lot of photographs from their Spy and Private-Eye Museum. Some are too small to be useful, but clicking through will find you many gems.
The Propnomicon blog has a number of posts on paper props.
A great source for researching vintage ephemera is eBay. Though it can be hit or miss, it’s one of the few sites where hundreds of people are uploading photographs of actual historic relics. You can search for your specific prop need, or search for “vintage ephemera“, or browse the Collectibles category.
You can also find a large number of actual historical documents online, which you can adapt for your use. For example, say you’re dressing a New York City apartment building, and want some realistic documents hanging in the lobby.
If you go to the Department of Buildings, you can search for specific buildings, and find a scanned copy of the actual certificate of occupancy. For instance, I can search for 940 St. Nicholas Avenue in Manhattan, and click on the “View Certificate of Occupancy” link, which will present me with a PDF of the actual certificate of occupancy. Government websites, while notoriously difficult to navigate and search, can often contain a treasure trove of historically accurate and specific documents.
Genealogy websites are a great place to find all manner of scanned copies of original documents, such as birth certificates, ship manifestos, census records, et al, but unfortunately, most of them require purchasing a subscription for access to their records.
If you do enough searching, you should be able to find an actual document to adapt, or a clear picture which you can replicate. You may wish to include historical photographs in your document; in an earlier post, I showed how you can use Flickr for visual research.
You may also need to edit the document to add your own text. If it needs to be handwritten, you can do it yourself (or ask someone with good penmanship to do it for you!) If you need multiple copies of this, you can scan it in and print out however many you need.
If your paper prop needs something typed, you’re going to want the proper font. I keep coming back to DaFont as one of my favorite sites for fonts. All the fonts are free, they’re well categorized for easy searching, and the site allows you to enter your own word or phrase to preview in all the fonts.
Even after creating your paper prop, you may wish to age or distress it. There are a number of ways to do this. Curious goods has a great tutorial on aging paper. Another good description of aging techniques can be found at Cephalopod Productions. Santiago’s Magic Musings has a post which lists some additional paper aging techniques. If you wish to age photographs, rather than documents, the previously mentioned Propnomicon has a post on that as well.