Encrypted PDF Files Opening Blank in iOS

Dear Members,

I have an encrypted PDF file with OTP protection using AES-256 encryption and send to users through email as attachments.

These files opens successfully on:

• Windows
• Android
• MacOS (Catalina 10.15.3) - all browsers be it Safari or Chrome

These file open as blank on any mobile/ipad iOS as well as MacOS Document Viewer and right now testing is being performed on iPhone 7 running with 13.3.1 iOS. This has been tested in Chrome as well as Safari and even "Open With" option doesn't seem to be working at all:

• iBooks -> it keeps on prompting password again & again;
• Adobe Acrobat -> keep saying "Opening" with endless progress bar.

Only option working in iOS devices is of saving this file to device and then opening the same with Adobe Acrobat.

Any help/pointers towards solving this problem will be highly appreciable.

Thanks,

Shaurya Jain