How would I cite/reference an electronic manual obtained as a PDF?
Answer
If the manual is a full book, follow the directions for citing an electronic book. The format would be the same for author, year, title, and publisher, but you would include a retrieved from and insert the URL as you would for an electronic book.
Look at the Library's Citing Sources page. The Purdue OWL, a respect source on citations, has many examples of unique electronic resources and how to properly cite them.