A new feature of Wikipedia is called Wiki Books that you can create from within wikipedia itself. You collect a number of wikipedia articles that you want to turn into a single pdf file (the book), place them in a userpage in a folder /Books/ and hit the - load book - link. It is really that easy. The app behind it breaks up the book into chapters and takes care of an index, page numbers and takes care of layout issues. At the end of the book there is a list of article sources (specifying the edits) and contributors. The Image licences and general licence are also taken care of. As an example of a wikibook, this blog has helped to create the definitive work on isomerism:
Open here: Wikibooks/Isomerism.pdf (8.5 MB)
With 120 pages and 8.5 MB it contains everything you need to know of trans isomers, enantiomers and tacticity. Several hundreds of editors have contributed and are listed in the back. Important note: the wikibooks folder does not allow search engine crawlers: no search engine pollution!.
Wikibooks is a great way to curate wikipedia. Especially in the chemistry desk the number of volunteers is dwindling and at some point the quality of information can no longer be guaranteed. By offering wikibooks from a separate entity there is at least a backup. Next up: The Wikipedia Handbook of Organic Reactions.