Answer 1

its been a while since i use Inno Setup, so i'm sorry if its not quite right.
open the .iss file

find section called [icons] or something like that, you should see the setting for shortcut to your program and uninstaller here.
just follow their format as an example, but at the Filename change it to your documentation file

ex: Name: {group}\documentation; Filename: {app}\help\docs.pdf

Answer 2

i no longer develop desktop application, but i remember i was using either InnoSetup or NSIS.