Shortcut MacOS to go to the beginning of a document Specifically as an example, I have a pdf document with 1000 pages and I'm in the page number 400 .. I want have a shortcut to move to the page number 1 and the page number 1000 ...

Is there any keyboard shortcut In MacOS to move to the begin and the end of a document no matter which third party app is running such as a pdf Reader, word document or any other software?
AFAIK, there is no universal shortcut. But Preview provides for this with the "home" and "end" keys (on an extended keyboard). Another handy Preview shortcut is CMD-OPT-G, which brings up a tiny dialog where you enter the page number you wish to display.

For Word, or other apps, you might try creating your own shortcuts: System Prefs > Keyboard > Shortcuts . . . App Shortcuts.

G'luck.