The guide document linked above will download as "Texture_Tutorial.pdf"
Inside the PDF, there is a direct link to the included collection of downloadable textures:
Just because I’m a giver, I’ve created a never-before seen, exclusive collection of textures for you, dear reader! One-of-a-kind, made by yours truly. Yours for you to use, royalty-free, ad infinitum, ad perpetuam, pro gratis, forever. You get the picture. Go get the texture collection (in ZIP format):
Just a quick note: I've modifed the document to reflect a change in the hosting of the collection. It's now at my Google Drive. (Click the link to get the collection directly. The tutorial itself has not changed.)