Referencing pages of articles and books
The right page number to use is the formal page number in the larger volume, even if the actual PDF that anybody will ever download is only a few pages long.  That is because a citation is intended to give the "coordinates" of a document in an absolute and access-independent reference system.

Thus, if you are referencing an article that was published as page 374-382, then its 2nd page is page 375.  You can also refer to page ordinally in prose, however, in which case you make the reference point explicit and can start wherever you want, e.g., "the third page of the article", "the second page of Section III".