Answered By: Mary Ann Naumann Last Updated: Jan 17, 2018 Views: 13793
The APA Style Blog provides some guidance and examples:
Page Range Example from PLoS ONE
No Page Numbers example from Frontiers in Psychology
"Several online-only journals publish articles that have article numbers rather than unique page ranges. That is, instead of the first article in the issue starting on page 1, the second on page 20, the third on page 47, and so on, every article starts on page 1 ... simply include the page range as it is reported for the article in your APA Style reference. The page range may be listed on the DOI landing page for the article and/or on the PDF version of the article ... If the article is published in a format without page numbers entirely, just leave off this part of the reference (i.e., end the reference with the volume/issue information for the article)."