You must first deposit your preprint on a preprint server, such as bioRxiv or PaleorXiv, to obtain a DOI.
Your preprint must not be published or under consideration for publication elsewhere at the time of its submission to PCI Paleontology. If your preprint is sent out for review by PCI Paleontology, you are not permitted to submit it to a journal until the PCI Paleontology evaluation process has been completed. You cannot, therefore, submit your preprint to a journal before its rejection or recommendation by PCI Paleontology.
You must be aware about the timing of the process. It takes:
up to 20 days before a recommender decides to handle your preprint and therefore to send it out for peer-review.
a mean time of 50 days before a recommender takes a decision based on the first round of peer-review
The evaluation of your preprint might take several rounds of review before the recommender take the final decision to reject or recommend your preprint.
Details about the evaluation & recommendation process can be found here