How do I cite an article with no page numbers and only a DOI number (APA format)?
According to the 6th edition of APA:

When using the exact words or a close paraphrase or summary of a source, a page number must be provided as part of a complete in-text citation. However, some publications (such as websites) have no numbered pages. To help readers locate the words being cited, include one or both of these elements:

Paragraph number (counted by yourself or as indicated in the text)
Main heading or sub-heading within the text (if available and appropriate)


So, if you are using a direct citation the approach with manually counted paragraph number and sub-heading section is recommended. The link above provides the following example:

According to the 2012 Canadian Survey on Disability, “[o]ver 11% of Canadian adults experienced one of the three most prevalent disability types: pain, mobility or flexibility” (Statistics Canada, 2013, para. 2)


However, if you are referencing for a purpose other than direct quotation or a close paraphrase, you can simply use 1–N, where N is the number of pages in the cited paper:

Simon, S. L., Field, J., Miller, L. E., DiFrancesco, M., &amp; Beebe, D. W. (2015). Sweet/dessert foods are more appealing to adolescents after sleep restriction. PLoS ONE, 10, 1–8. http://dx.doi.org/10.1371/journal.pone.0115434