Actually editing PDF files is, unfortunately, quite difficult. (Technical reasons. I'll elaborate if people want to know).
You could create your own store labels; an easy way would be to use Google Docs.
Under the "font" drop down is a list of boring fonts and... "More Fonts". If you check "Display Fonts" and scroll down the list, you can find all sorts of neat stuff for labelling western buildings. There's a search box if you know what you're looking for; Try "Ewert", "Asset", "Smokum", "Trade Winds", "Peralta". Or just browse.
There's an image drawing tool in there if you want to add frames/borders etc.
If you really want to edit the PDF files like this, the easiest way is to create a new PDF with the elements you want and then overlay it on the other one, then print the resulting PDF. There's a free tool called pdftk for doing that sort of thing -- I use it to print unit stats into "blank" record sheets for example.