Viewing PDF files in your Web browser or in free software such as Adobe Reader gives you access to everything from magazines and catalogs to tax forms and educational materials. In its early days, PDF lacked some of the format's current flexibility, including its online functionality and its free access through readily downloadable applications. Today's PDF readers may lack the $50 price tag of 1993's initial version of Acrobat Reader, but the file format's many advantages come with some drawbacks, too.
The Portable Document Format makes complex, graphically rich content accessible to just about anyone with a computer, regardless of the operating system you use, the applications you run, the font files to which you have access and whether your computer can support the tools necessary to open the original documents that PDFs represent. To achieve these objectives, the file format must lock down most aspects of its content and serve them up from embedded assets that you can't edit or embellish more than superficially. When you prepare a PDF with its graphics at full resolution, the resulting potentially large file can serve as a press-ready resource for commercial printing. With its graphics downsampled and compressed, a smaller version of the same file can serve as an online-viewable resource, but the compromises you must make to reduce file size also reduce the fidelity of bitmapped graphics.
Adobe Systems incorporates document security features into its Acrobat applications so users can protect various aspects of their intellectual property. For overall security, you can require a document recipient to enter a password to open a PDF file and a separate password to override security features. Within PDF security settings, you can restrict individual aspects of document alteration and processing, allowing a file to be printed -- in low or high resolution -- or preventing it from printing at all, and disallowing the addition of comments and annotations. You can override the ability to copy or extract pages from the file and even protect a PDF that contains form fields against data entry. However, these security provisions may not deter a determined individual who obtains tools that can override them.
When you adopt document security policies that enable others to comment on a PDF file, the members of your workgroup can collaborate on project revisions within a PDF version of the document itself. PDF markup tools enable you to add typed or handwritten notes, mark directly on a page to question the inclusion of document content, crop document dimensions and mark out sensitive material for redaction. You can work your way through a document from one comment or revision note to another using interface features built into Adobe's Acrobat applications. Unlike the on-paper equivalents of these digital notes, however, the PDF versions can be time consuming to process because they can require you to zoom in and out of and scroll through pages to review all the annotations.
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