There is a possible negative effect of adding new pages to your site.

Take a perfectly normal site. It has some inbound links from other sites and its pages have some PageRank. Then a new page is added to the site and is linked to from one or more of the existing pages. The new page will, of course, aquire PageRank from the site's existing pages. The effect is that, whilst the total PageRank in the site is increased, one or more of the existing pages will suffer a PageRank loss due to the new page making gains.

Up to a point, the more new pages that are added, the greater is the loss to the existing pages. With large sites, this effect is unlikely to be noticed but, with smaller ones, it probably would.

So, although adding new pages does increase the total PageRank within the site, some of the site's pages will lose PageRank as a result.

The answer is to link new pages is such a way within the site that the important pages don't suffer, or add sufficient new pages to make up for the effect (that can sometimes mean adding a large number of new pages).

Otherwise per every X new pages you add to your site, you are going to need X*Y additional inbound links to maintain PageRank for your site pages.

I think this is just another reason why it's important to acquire links to internal (product) pages of your website and not just the homepage.

People forget Google ranks "pages" and not "websites"