Portable document format (PDF) files remain a popular choice for business documents ranging from contracts and forms to manuals and reports, so there's a good chance you need to open them often.

Q: Sometimes when I try to open a file or e-mail I get the message: "The selected file has an extension (PDF) that is not recognized by Windows Media Player but the player may be able to play it.

The software Google's browser uses to show PDF files has been proprietary for years, but now it's an open-source project called PDFium that others can scrutinize or use themselves. Stephen Shankland ...

PDF files are a mainstay in our multi-platform world. This convenient file format makes viewing and sharing documents across various devices using various operating systems and software programs ...

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