lost of list of user selected PDF files of task bar icon

>Maybe it is a language problem
partially, the adj "lost" was used as noun "loss" 

i write with errors even in my native language, but do not for very limit of sense loss (ah, i want to say "lost" there, the bad habit). And more, i guess you have lied here to get a kind of profit, consider:
for
>> Last installed adobe reader DC
you wrote
>Are you trying to install Acrobat Reader?
in some political system it is not a crime to lie and steal everywhere, but a way to be rich (it is prohibited by both: ancient human moral ideas; and developments of moral ideas as civilisation progressed). 

>but your post 
just was intended for adobe reader writers (writers are the guys who write "install" program for win (win means windows), there are no other bug or feedback directories, even the forum works not in all browsers). 

>And what does having a list 

i say "the list was pinned to adobe reader icon in task bar" ("to pin file of suitable type as user selected to app icon that is placed in task bar" is well known user feature of taskbar of win explorer (aprox from vista times); taskbar is: google-> https://www.howtogeek.com/77614/best-windows-7-start-menu-and-taskbar-tips-and-tricks )

>Is this an Acrobat Reader problem? 

sure 

Install program sould process user lists, icons and settings with care, the desktop shortcut or start menu link can be placed by user in its personal folder (no need to move it into public one) etc. 

note: it is known the selected list is not very reliable system (it is often damaged) but install program should not delete the list with intention, i lost my "list of contacts" by safe action (by update of version of the same software), it was not a poison thing but unexpected.