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PDF: The Cure for Dawdling Digital Files

(December 1999) posted on Tue Dec 14, 1999

Learn the basics of creating PDF files.

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By Mark A. Coudray

Acrobat Reader (free) Once a file has been converted to PDF, it must be viewed with either Exchange or Acrobat Reader 3.0. Older versions of Reader will not work on files converted to PDF with Acrobat 3.0. PDF files can be viewed and printed from Reader, but not edited. Reader is available at no cost from Adobe's Web site ( and will operate on any computer platform.


Benefits of PDF


Since PDF files are true PostScript, they are resolution independent. This means that we have the option to specify at what resolution the final document will be imaged. It may be a low-dpi device like a laser printer, or a high-resolution device like a laser imagesetter. The maximum resolution we can choose is 2400 dpi. The default settings in Distiller are 72 dpi and are intended for computer viewing, so they must be changed.


When preparing original files for Distiller, follow the usual and customary rules for halftone scanning resolution. Most commonly, this means using an image resolution that is twice the value of the desired output halftone line count. For instance, if the halftone needs a printed resolution of 100 lpi, the scan data should be 200 dpi. Monotone elements (primarily type) should be set for 1200 dpi or the highest resolution of your output device. For screen printers, this could be 300, 400, 600, 800 dpi, or higher. The device output resolution determines the settings we'll use in the Job Options dialog box under the Distiller Menu.


Preseparated or composite files


You have two file-type options in preparing the final PDF document. They are Preseparated and Composite. Preseparated files are larger and cannot be viewed by the end user. They are preseparated for output as color separations. One PDF page is generated for each color that is to be printed. So if our design includes CMYK plus one spot color, the preseparated file would contain five pages. This option makes for larger files, but it allows you to print spot color gradients, DCS files, duotones, tritones, quadtones, and colorized TIFF files.



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