Dov Isaacs, principal scientist in Adobe's Print Workflow Products Group, outlined his principles in a workshop at the Adobe Acrobat PDF Conference here.

The first principle, according to Isaacs, is, "the quality of an end-product directly reflects and can be no better than the quality of its source components." Taking care when selecting, preparing and assembling ingredients for a PDF is a key to success, Isaacs said, and he recommends that companies get professional training for those involved in the process.

Isaacs' second guiding principle is: "Maintain content at its highest level of abstraction by category and within category." If information is in text form, it should be kept in text form for maximum flexibility rather than being converted to a vector graphic. Likewise, graphics are easier to manipulate than raster images, and live transparency and gradients are easier to control downstream than flattened transparencies and gradients are.

The third principle, according to Isaacs, is to "lose no data before its time. Add no unnecessary data." When fonts are converted or image data is downsampled then upsampled, the quality of the data deteriorates, he said. Likewise, color information should not be converted to device colors until late in the game.

Isaacs' fourth principle: "Avoid unnecessary and cascading data and attribute transformations. If you need to rotate a graphic, for example, "rotate it only once, at the end," Isaacs said.

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The fifth principle, he said, is, "Problems detected earlier in a workflow are generally easier and less expensive to correct than equivalent problems detected later in the same workflow." Technical problems detected while in an authoring program are easier to fix than problems found in Acrobat or on a printing press, Isaacs added. He emphasized the point by applying his fifth principle to aviation: "Would you first go over the 'preflight' checklist at 40,000 feet?"

Isaacs sixth principle is, "Disciplined use of standard operating procedures for a workflow is a major success factor for consistent production and hence, reliable production."

Isaacs also talked about the three different methods of creating PDF files and the best uses for each.

Creating PDFs via distillation of PostScript can be done from any application that has a print function that can work with the standard, system PostScript Driver, but it is difficult using this method to create PDFs with advanced structure, linking and multimedia features, he said.

A second method involves generating PDFs directly from the operating system, but the only implementation is in Mac OS X. This method is potentially the most efficient but offers limited configurability.

PDFs also can be created through direct application export, which is also a fast method that can create relatively compact PDFs. This is the preferred method of PDF generation with Adobe's InDesign, Illustrator and Photoshop and can maintain live transparency and ICC color management, Isaacs said.

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