I briefly scanned the paper. The above summary is garbage.

For a biologist, a summary might be like this: pcr fragments are generated with short reverse complementary sequences added to the end of one fragment that match that at the begining of the next to-be-joined fragment.

These will anneal to create a cross-shaped DNA molecule. The short arms of the cross being the complementary sequences. Like so:

  ======∥=====

The short arms can then be processed-off to leave behind the now-longer fragment. The process can be repeated using different reverse complementary sequences between each fragment, the "page numbers" referred to.