Julie Shaffer is Director of the Center for Imaging Excellence. She presented the “Meet the Perfect PDF” presentation at “Momentum in Print”. Shaffer started with explaining what a “perfect” PDF is. The perfect PDF is one made with the final output in mind. That implies there are as many perfect PDFs as there are usages for them: office print, high-end lithography, display, soft-proof, multimedia, web-ready form…
One idea that Shaffer launched is that poor quality original content will always result in poor quality PDF, but good quality content files can also result in poor quality PDFs if they aren’t created properly with the intended output in mind.
Shaffer gave the recipe for perfect PDFs. It carries eight ingredients of which the last one she seemed to find the most important: preflighting. She went through all of the ingredients, starting with the question where PDfs come from. Contrary with where babies come from, the answer was diverse: from Adobe distiller or Jaws, QuarkXpress, PDFMaker, or Mac OS X Preview which has a Normalizer built-in.
Other originators of PDF files—with varying success quality-wise—are Adobe CS applications, prepress and desktop publishing workflows, other DTP applications such as Canvas X, and Freehand, and Microsoft Office 12. Even Mac OS X can be the originator of a PDF, through the “save as PDF” option. Users can even ‘enhance’ these PDFs with Quartz filters.
The best PDF file
Except for the Quartz filters in Mac OS X—which aren’t understood by DTP applications at all—almost every method can create good PDFs. But there are differences, although not always those that you would expect the most.
For example, printers will always trust PDFs generated by a Postscript interpreter. But, if Postscript can’t handle it, the PDF will not contain it. So transparency will be flattened and a colour conversion will happen to device colours. Fonts may be converted as well. TrueType fonts may be encoded as Type 1 fonts.
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Direct PDF export is best when the original data must be kept intact. Again, transparency is an example. However, Shaffer said, someone downstream will have to deal with it. Nevertheless, direct PDf export has its advantages. Users don’t have to rely on the limits of printer dialogue setups, and CS2 products can share Export presets anyway.
Mac OS X’s PDFs are the least suitable for all-round PDF work. They are not optimised for high-end printing, there is the problem with Quartz filters mentioned earlier, and EPS vectors result in bitmaps. Also, spot colours and device N colours won’t work.
10 problems with PDFs
Shaffer than listed the top ten problems with PDF files.
- Image resolution too low
- Fonts not embedded
- Wrong colour space
- Incorrect trim or bleed information
- Inconsistency with native file (hairlines, gradients)
- Spot colour misnamed or converted to process colour
- Too much compression (artifacts, quality loss)
- Incorrect page size information
- Transparent object issues
- Incorrect or missing ICC profile
Best practices can help avoid these, according to her. Best practices are PDF/X standards. “With a PDF/X checking mechanism in place, content receivers will know that the file is much closer to ready to image,” she said. But several versions of PDF/X exist today. They differ based on workflow and usage.
PDF/X-1a is based on PDF 1.4, and is a CMYK-only blind exchange format. There is no live transparency, fonts must be embedded and some compression types cannot be applied to their fullest.
PDF/X-3 is a superset of PDF/X-1a. It also allows colour-managed data with ICC profiles, but just like x-1a, there is no limit on image resolution.
PDF/X-2 is a superset of X-3. It favours an open exchange, an OPI-like workflow which allows for linked external files, proxy images, etc.
Finally, the future may bring us PDF/X-4 and X-5, which will be based on PDF 1.6. These versions will allow live transparency, layers, the embedding of OpenType fonts, 16-bit images and external links.
Shaffer ended her presentation with a focus on preflighting. She said there’s no excuse for not preflighting as it can be done almost anywhere these days: in the native application, stand-alone, in Acrobat, via PDF creation and via the Internet as part of FTP delivery.
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