The document summarizes discussions from a workshop about reducing uncertainties in parton distribution functions (PDFs) that affect measurements of the W boson mass. Key topics discussed included issues modeling the Z boson's transverse momentum, inconsistencies between PDF sets, and the need for additional LHC measurements like of W/Z production to reduce PDF uncertainties in future W mass measurements to below 10 MeV. Participants agreed more work is needed to understand differences between PDF sets and include relevant LHC data in global fits.