The change in the pore structure of paper fibers during during either during paper forming process or at the individual fiber level is a topic that has been widely studied by paper science institutes around the world. You can start with TAPPI, or Institute of Paper Science and Technology in the US, or the Canadian equivalent, or the Swedish Pulp & Paper Research Institute
I currently work in a pulp and paper research institution. We don pulp analysis and even paper tests in our pulp and paper labs. We have a number of publications on pulp and paper and I suggest you look at TAPPI methods which will offer you more about what you're looking for, other than to read research papers which give more extensive results based on those tests.
If you join TAPPI (www.tappi.org), you get free access to download technical papers from their data base or, as a non-member, you can purchase the ones you want.
North Carolina State University (NCSU) has a peer reviewed online journal called "BioResources" where you can download technical papers - http://www.ncsu.edu/bioresources/