New life for old acrobat

Since its introduction, Adobe's Acrobat has been the most popular software product for allowing users on different computer systems to read each other's files. But these days, Microsoft Word is so common that it's a de facto exchange format, and Word documents can be modified, whereas, until now, Acrobat files could not.Adobe had some catching up to do if Acrobat was going to survive.

With Acrobat 4.0, Adobe breathes new life into an application that was threatened with obsolescence.This most recent version, released last month, takes the product in healthy new directions.

You can now digitally sign Adobe Portable Definition Format (PDF) files so recipients can verify they haven't been modified. A recipient can annotate or add to the...