How should I do MLA in-text citations if some of my sources have page numbers and others don't?
The rules for MLA in-text citations acknowledge that in some situations with web publications there are no page numbers available. In these situations, the in-text citation can only include the author's last name. However, whenever a document has page numbers you should document it in the in-text citations.
Therefore, it's okay for a paper to only include the author's name in some in-text citations (the HTML document) and include the name and page number in others (the PDF document). Just be consistent -- omit the page number only when it is impossible to determine the page that the information you are citing comes from.