How you access an online work will affect how you document it. For example, if you access a PDF from a Web site, you need to provide full publication information for the PDF in the first container and publication information for the Web site from which you downloaded the PDF in the second container, as in the example below for a report on the MLA Web site. At the end of the entry, you might include “PDF download” in the optional-element slot to make clear to the reader that the URL does not take you directly to an html version of the report.
Executive summary. Report of the Task Force on Doctoral Study in Modern Language and Literature, Modern Language Association of America, 2014. Modern Language Association, 2017, www.mla.org/Resources/Research/Surveys-Reports-and-Other-Documents/Staffing-Salaries-and-Other-Professional-Issues/Report-of-the-Task-Force-on-Doctoral-Study-in-Modern-Language-and-Literature-2014. PDF download.
Let’s say, however, you link to a PDF directly from a bibliography or an e-mail sent by a teacher or colleague. In that case, it is usually sufficient to provide the URL that leads to the PDF as the location of the work and to omit a second container:
Executive summary. Report of the Task Force on Doctoral Study in Modern Language and Literature, Modern Language Association of America, 2014, www.mla.org/content/download/25438/1164362/
If you are an editor checking an author’s works-cited list, follow copy.