I hope you're doing well. Can you specify that you're using the Acrobat reader desktop application or the acrobat reader mobile?
Also, for a better understanding, can you share a video of the workflow you're doing, so I can assist you better?
To know how to delete any pdf, you can use this article-
Let me know if this helps.
Sorry for the trouble.
Would you mind letting me know a few pieces of information:
1. The application version you are using for Acrobat Reader Mobile;
2. The operating system version of Android you are using;
3. The file you are trying to delete, is it in your phone storage, adobe cloud storage or any other cloud storage? Deleting other cloud files than Adobe Cloud Storage can cause issues too.
Looking forward to hearing from you.