You need to clear the cq:distribute property on author instance before the PDF gets replicated back to publish instances. This is mentioned in the documentation of reverse replication-
Make sure that you clear the cq:distribute value in your workflow, if you reactivate the content on author to the publish, otherwise it goes in an endless loop !!!
https://helpx.adobe.com/in/experience-manager/kb/HowToUseReverseReplication.html
I will recommend you to use Sling Content distribution rather than reverse replication as sling content distribution is more reliable and with it you will never see endless loops. Also, it is built for future and is supported in AEM as a cloud service offering. The reverse replication mechanism will not work in cloud service version as it is not supported.
https://experienceleague.adobe.com/docs/experience-manager-65/administering/security/sync.html?lang=...
https://medium.com/tech-learnings/sling-content-distribution-in-aem-part-1-35158614dc53