For Position Only: Preserving Transparency in PDF Workflows

Anita Dennis

3

Designers love transparency and transparent effects — the digital panache that comes from gradient meshes and blending modes. Transparent effects combine the colors of all the pixels in a stack, instead of just the topmost opaque pixel. But if designers love transparency, I’ll bet you dollars to donuts that your prepress provider doesn’t. In PostScript workflows, transparency can be hell on RIPs, and documents that contain transparency must be flattened — the effects must be irreversibly calculated and the final object rendered opaquely — before the PostScript file can be rasterized.

So when a vendor like Adobe goes and makes its applications’ support for transparency increasingly robust, what’s a designer to do? Well, keep using transparent effects, of course, but manage them wisely. Here’s the skinny on how you can do that with PDF.

The Old Way
Traditionally (if there is such a thing as “traditional” digital workflows) we routinely flatten artwork when we finish creating it in Photoshop or Illustrator. We do this by saving artwork as EPS or TIFF before we place it in a page-layout application (or some of the more adventurous among us would distill a PDF file of the artwork and place that in the page-layout application).

But either way, that means those files are finished, done, final. You can view the transparent effect when you’re working in the page-layout application, but it’s been flattened. If clients decide when they see a page-layout proof that they want a change in the artwork, this old workflow meant returning to Photoshop or Illustrator and editing the original file, flattening it again by resaving or re-distilling it, and then replacing it in the page layout application.

The New Way
But there’s a new-and-improved PDF workflow if you’ve got Photoshop 6.0 (or later) or Illustrator 10 and InDesign 2.0 — you don’t even need Acrobat 5.0, even though this new method of keeping live transparency involves using the PDF 1.4 spec that is new with Acrobat 5.0. What you do is choose Save As from Photoshop or Illustrator’s File menu and generate a PDF 1.4 file using libraries that come with those applications. Because these saved PDF 1.4 files don’t go through Distiller, they don’t get flattened, so transparent effects are preserved and you can go back and edit them in the PDF format.

Don’t be confused like I was for a long time: Whether you distill or export to PDF 1.4 or an earlier version of the file format, you’ll be able to see the transparent effect in Photoshop, Illustrator, InDesign, and Acrobat, but you must export to PDF 1.4 using the Save As command to actually be able to go back and edit it.

So in this new workflow, when the client wants a change to the artwork after reviewing a proof of the page layout file, simply open the PDF artwork file in Photoshop or Illustrator and go to work: Your layers will be intact. You can move or edit the objects, add new ones, do whatever is required, and then simply save the file when you’re done — not Save As and wait for the file to flatten to EPS or TIFF, not twiddle your thumbs while Distiller produces a new, flat PDF. Just Save. Then re-open your page layout file in InDesign, click Fix Links when prompted, and voila: The revised artwork is in place, looking beautiful — and still editable if need be.

The Gotchas
Got it? Good. Now here are the catches: There’s a certain page-layout application (I’ll give you a hint — it’s not an Adobe product — and one guess) that doesn’t support transparency or PDF 1.4 import. If you place a PDF 1.4 file with transparent effects in a QuarkXPress document (or InDesign 1.5 or earlier document, for that matter), you won’t even be able to see the transparent areas onscreen in those applications. You’ll see flat, opaque areas instead of blends or gradients. So to maintain your transparent effects when placing artwork in XPress, you still have to flatten it first by saving as EPS or distilling to PDF. This means sticking to the old workflow and not being able to work with live transparency in PDF files (and in my mind, this is one more reason to switch to InDesign).

Macromedia FreeHand and CorelDraw also have limited support for PDF 1.4 and transparency. Illustrations created in those applications can be distilled to PDF 1.4 or exported to PDF 1.3 or earlier, flattening transparency via either method. And neither program lets you import a PDF 1.4 file, much less edit any of transparent effects in such a file.

Finally, a minor point to keep in mind is that when you’re exporting PDFs from applications remember that the final file will be the page size as defined by the document, not the page size as defined by the printer driver. Usually that’s fine — even better — for PDF artwork that will be placed in a page-layout application: Your 2-inch-square logo won’t be surrounded by white space to fill up 8.5 by 11 inches.

The Upshot
What all of this boils down to is that if you want to use the editable transparency capabilities in PDF 1.4, for the time being at least, you have to work in a choice set of four Adobe applications: Photoshop, Illustrator, InDesign, and Acrobat. Someday we may have more flexibility, but it could be worse.

Regardless, there’s one very important final caveat: Be sure to Distill your final page-layout file to create the PDF that you will hand off to your prepress provider or printer. While Adobe has made editable PDF a nice image file format for the design phase of a publishing workflow — at least within its own suite of applications — all files that are destined for a RIP should be flattened and normalized by Distiller. If you have any doubts or concerns, check with your prepress provider.