Copying of any text is subject to copyright law.
For the sake of simplicity and to be future-proof, documents should be in plain text. If you are really ambitious you might also want to create a version marked up in one of the standard xml structures. The format of current word-processor documents will not be readable in a few years time, so it's not a great idea for a library..
Copying anything published less than 70 years ago is almost certainly illegal unless you have permission. Short extracts probably comply with the "fair use" copyright law (a safe rule of thumb might be less than 1% of the full work).
If you have permission from a right-holder, or if you have text for which you are the right-holder, we'll be happy to put up a link.