You open a PDF in Safari first, then when it opens, send it to Reader.
[topic moved to Reader/Acrobat for mobile forum]
You cannot paste a hyperlink into the Adobe Reader/Acrobat DC for iOS app. But I think I understand what you want to happen.
When you tap the hyperlink (to a PDF document) in a email message or web page on your iPad, the PDF document will be opened it in Safari. You can use the iOS "Open In' feature to open it in Adobe Reader/Acrobat DC for iOS.
Please see the Safari section of the following FAQ document to see how to use "Open In".
Once the PDF document is opened in Adobe Reader/Acrobat DC for iOS, you can add annotations (e.g. Sticky Notes, Highlight, Freehand Drawing), fill in (if it's a PDF form), print, and perform other operations.
Please let us know if it works for you. Thank you.