If no date can be established you can use n.d.
If the date can be established but only approximately you should use c.
Electronic books read via an e-reader such as the Kindle do not have traditional page numbers. In this case, if you need to use a quotation from this source, use the chapter numbers for indicating the location of the quoted section:
If you wish to cite a web resource that does not include page numbers, you can include any of the following in the text to cite the quotation:
• A paragraph number, if provided; alternatively, you could count paragraphs down from the beginning of the document:
• An overarching heading plus a paragraph number within that section:
• A short title in quotation marks, in cases in which the heading is too unwieldy to cite in full:
A PDF is a format rather than a type of resource. You should reference this according to the source type, but if this is not possible, you can reference as a website.