There are only 3 ways for an article to appear in PubMed:
1. If the article is published in a journal that is indexed for MEDLINE.
2. If the article is published in a journal that is accepted for PubMed Central.
3. If the article is grant funded by a funding institution that is accepted by PubMed.
Note: In January 2019, PubMed revised their policy for including Open Access articles in PubMed. Until December 2018, all Open Access articles published in Springer Nature journals were automatically included in PubMed. After the revision of this policy from January 2019 onward, articles published in MEDLINE indexed journals are included in PubMed.