Creating a PDF (Portable Document Format) document means to store one or more digital documents in a graphics format. This allows text, tables, and images to be packed into a single compressed file. Converting a PDF means to reverse the process and transform the graphical image to a reproduction of the original digital document. A "searchable PDF" includes a hidden digital code, which allows a limited level of manipulation of the PDF image.

Adobe Reader, a free program provided by the inventors of this format, allows users to see the stored images, but not create or convert a PDF. Adobe Acrobat ($300) for Mac and Windows includes these capabilities with a wide range of options. Reader can be used to attach notes to a PDF, but only if the PDF itself is created in Acrobat.

Macintosh: Recent versions of Word for Macintosh include a "print to PDF" function that allows documents to be stored as PDF. Creativepro.com sells Jaws PDF Creator ($64), a high performance creator for both Mac and Windows, which creates Adobe-compatible PDF with numerous features including rearranging, underlining, attaching notes, etc. with Reader.

Windows: On the Windows platform, PDF creation and conversion requires the purchase of additional programs. A few handle PDF independently: for example, Photoshop will take an image directly from a scanner and store it as a single "flat" (not searchable) PDF. Any OCR reader (e.g., Omnipage) will read PDF text and convert it to digital characters, although the original formatting will be lost.

Most PDF creators install as printer drivers so that digital documents are "printed" as searchable PDF. The original resolution of graphics documents packed into PDF is usually preserved. NovaPDF ($29.95) creates PDF from any Microsoft application (DOC, XLS, TIF, PPT) in a folder of your choice. Internet addresses and URLs are saved as clickable links. Its PDFs can be further compressed as ZIP or JPG. PDFCreator ($29.95) is comparable.

Nuance PDFCreate! ($49.95) can combine material from all different Microsoft applications in a single document, and provides thumbnail previews. It also makes PDFs direct from scanners. Nuance PDF Converter (also $49.95) restores PDF images to original digital format.