Page cache and its relationship to page table
The only link is that they both operate with the same page size and, well, the same pages.

The reason is the mechanism of file access. You can request access to file via mapping its contents into memory space. In this case, the entire file isn't read into memory at once, instead, the page table is filled with inaccessible pages. Once application tries to access these pages, the actual file contents is read into memory.

So, the file cache stores individual pages of files, and this mechanism is described in the page cache article.