How many pages?

[SlowMove]

I put 2000 new pages on a PR4 site, and all of a sudden, the home page and about 20 others are PR5. If I keep adding pages, will PR continue to increase? Is everything that happened a result of external links, and is there a limit as to how many pages Google will index?

[pixel_juice]

>>I put 2000 new pages on a PR4 site, and all of a sudden, the home page and about 20 others are PR5

The two events are unconnected. The pages you added all start off with no pagerank at all, and so if anything extra pages mean that the PR of your site is spread more thinly across all the pages.

Your pagerank has increased as a result of additional incoming (external) links to your site.

>>is there a limit as to how many pages Google will index

There may be a theoretical limit, but Google currently lists 2,250,000 pages under Amazon.com, so pretty much anything is possible ;)

As a rule of thumb, the bigger (i.e. the higher the PR) the site, the more pages are likely to be indexed.