These are a bunch of sample documents for use with the book Painless Vim.
Either clone the repository:
git clone https://github.com/PogiNate/Painless-Vim-Samples.git
Or just download the zip and extract it somewhere that's easy to get to. The book will tell you which sample to use, and the in-text examples will include line numbers so you can follow along at home.
If you have any questions feel free to submit an issue on this repository.