The PDF/A specification for long-term preservation of electronic documents became an international standard in 2005. This standard seeks to guarantee the long-term visual appearance of an electronic document. For collections to be archived as PDF files, it makes sense to select the PDF/A file format, because this particular type of PDF file makes it easier to migrate to future file formats. However, in the years before the PDF/A specification became a standard, many organizations began creating archives of collections in PDF, but in formats not necessarily compatible with PDF/A. Because of its value to preservation that PDF/A offers, there is an advantage to migrating collections to PDF/A. Commercial software tools are becoming available, both for creating PDF/A files and for evaluating their compatibility with the PDF/A standard. One such tool was used to study PDF files culled from the Internet as well as from an in-house collection to determine the chances of success for migrating an archived collection of PDF documents to PDF/A. This study explores the types of problems posed by such a migration, and determines the circumstances in which a migration would be successful.