Maximum number of pages on iPad, and maximum apps in a folder? For some reason, after I installed many apps (because a company made them free Apr 27 to 29), and then, the icons don't appear at all, and there was no warning.

And I started to wonder, are there maximum number of pages?  And so I created some folders and put existing apps in them, and the other apps magically appeared. (I forgot if I restarted iPad in order to see them).

And there seems to be maximum 20 apps per folder.

I just wonder why there was no warning whatsoever given iPad and Apple products are usually very well designed and user friendly. Are there official pages that describe this situation?
There is a maximum of 11 pages of apps on your iPad.  Those that don't show up can be launched by swiping all the way left to the iPad spotlight, and searching for the app title.  As for maximum number of apps in a folder, I was able to fit 20 (as you mentioned). 

I was not able to find any official documentation regarding this matter.