Hi there! I understand you're having trouble opening PDF files in your AOL Mail on your iPhone. Let's work through this together.

First, could you please clarify if the PDF download attempt is showing any error messages or just simply not opening? Also, have you been able to open PDFs through other apps on your iPhone before, or is this the first time you're experiencing this issue?

In the meantime, here are a few steps that might help solve your issue:

1. Check Your Internet Connection: Make sure your iPhone is connected to a stable Wi-Fi or mobile data network, as a weak connection can cause download issues.

2. Restart AOL Mail: Close the AOL Mail app completely and then reopen it. Try downloading the PDF attachment again.

3. Update Your Apps: Make sure the AOL Mail app and your iOS software are up to date. You can do this by going to the App Store and checking for updates.

4. Clear App Cache (If Possible): Sometimes, clearing the app's data can help. Unfortunately, on iOS, this typically involves deleting the app and reinstalling it.

5. Download the PDF to Your Device: Instead of opening the PDF directly within AOL, try downloading it first. Tap and hold the PDF attachment in the email until you see an option to "Download" or "Save." Once it’s saved, you can access it through the Files app or a PDF reader like Acrobat Reader.

Let me know how these steps go! If you're still having issues, we can look into more advanced troubleshooting together.