In page 3 of PageRank paper is mentioned:
let c be a factor used for normalization (so that the total rank of all web pages is constant).
What is the use of
c and how can its value be computed?
The point of such a factor in general is that you want to be able to calibrate the scores you get, by forcing them to be within a specific range like $[0,1]$. In particular, this factor would be computed (in principle) by getting the rank of all pages and then dividing by their sum.