Decryption of large documents is realy slow.
When opening Large encrypted documents ( eg. 15.000 pages ) Acrobat is really slow compared to other PDF-readers. ( Soda/Foxit )
(large documents eg. 50.000 pages dosen't open at all.)
i have attached a realy simple large PDF document encrypted and signed - to illustrate the problem. ( opening time on my PC > 10 minutes - Other readers opens the file in < 30 Sec )
PASSWORD => owner
Adobe Acrobat Reader DC (2021.005.20060
( Same issue found in PRO reader. )