PAC Fairness Act of 2007 - Amends the Federal Election Campaign Act of 1971 to: (1) increase contribution limits for certain political committees, including multicandidate committees; (2) extend indexing of contribution limits for certain kinds of political committees to all political committees covered by the Act; and (3) revise requirements for the period of increase for contribution limitations, determination of the base year, permitted contribution-related communications between corporations and labor organizations and their members, and permitted contribution-related solicitations by trade associations.