It is interesting to read how other industries collect their bills. Many of the tips apply to reprographics:
Used car dealers practice tough love and don't hesitate to repossess when the bills aren't paid: http://www.autodealerpeople.com/profiles/blogs/improving-collections-in-your-bhph-portfolio
Accountants strive to understand their customers' internal processes: http://www.accountingweb.com/topic/accounting-auditing/pay-me-money-improving-collection-rates-step-step
Hospitals train the front-office staff to collect the co-pays upfront: http://www.beckershospitalreview.com/hospital-management-administration/8-points-on-improving-collections-of-outstanding-balances-from-patients.html
Companies working in emerging markets prioritize their collections based on risk, not age: http://blog.frontierstrategygroup.com/2012/06/3-strategies-for-improving-collections-efficiency-in-emerging-markets/
Dentists extract payment before the patient leaves: http://www.dentaleconomics.com/articles/print/volume-89/issue-9/features/strategies-for-improving-collections.html
Water industry professionals start with a written policy: http://www.watertechonline.com/articles/improving-collections-and-your-bottom-line
Manufacturers climb the ladder when bills don't get paid: http://www.fdcpa.com/M&D/0306NewsImprovingCollections.htm