With the flourish of online publications comes the need to reference these materials in such a manner that allows your audience to locate sources you cite. The American Psychological Association style manual provides guidelines for attributing references with in-text and reference list citations. PDF files found on the web will be cited as electronic sources, which follow a basic format. But some elements might change, contingent upon what your PDF source actually is -- an article or graphic, for instance.
Citations of electronic sources include the author, title, date and location where you retrieved the source, such as a website or article database. Here's an example of this type of citation: Manny, F. A. (1909). A study in adult education. The School Review, 17(3). Retrieved from http://www.jstor.org/
Instead of URLs, many journals include digital object identifiers, or DOIs, which will replace the “Retrieved from” and web address with “doi:” followed by the DOI link.
Graphics or Lecture Notes
For PDF sources like a graphic, use the following format: Organization. (Date of publication). [Graph illustration]. Project name (italicized). Retrieval information
A citation of lecture notes would include the professor’s name in place of the organization. After the publication date, include the italicized name of the notes, followed by “PDF document” in brackets to indicate the file format.