PDF application skills

A few years ago, according to the statistics of the United States Printing Technology Foundation (GATF), 88% of the surveyed printing companies and prepress professionals encountered problems in processing PDF files submitted by customers, and the methods were incorrect. There were 46 of them. % of people are trained on the actual operation of PDF, but there are still many problems. To date, there are still many printers that have obstacles in handling PDF files.

1. Transparency: End of Nightmare

For designers, "transparency" is a very useful tool, but many printing staff are very scratchy about files with transparent layers. For this reason, RIPs based on Adobe Postscript 3 (page description raster image processor) need to be improved to handle transparency issues, but many of the RIPs used today have not yet been able to upgrade to this level.

Fortunately, Acrobat 6 can squeeze transparency and print out the output file, otherwise it cannot be exported directly to RIP. Don't be fooled by the Transparency Flattener Preview command under the Advanced menu while processing. This dialog box is only used to preview the various effects of transparency on other objects in the file and does not produce true imagery. The effect is that transparency will not be truly flattened until the file is printed or saved in a Postscript file format.

(1) Open the "Print" dialog box, click on the "Advanced" option, view the "Transparency flattening" under the "Advanced Print Setup" command.

(2) When you move the slider to the left of the "raster", the transparency of all active areas will be flattened and the vector object will be converted to a raster object.

(3) Change the resolution of the default 300ppi “line and text” to not less than 1200 ppi. If the film is output at 2400 dpi, the 1200 ppi setting will have a good effect on low and medium resolution printing.

2. Rasterization of vector images

Before entering the production process to create PDF files, do not rasterize vector graphics. Usually people convert vector files to JPEG format. When the file is converted to format again, the file has a considerable degree of quality loss. The JPEG 2000 format as a conversion format minimizes the information lost in image compression.

3. PDF Writer and Distiller

Prior to Acrobat 6.0, PDF Writer was the best choice for creating PDF files. However, PDF Writer settings are not suitable for prepress processing, and Distiller is the best choice for PDF prepress applications.

After receiving the document, the most important task is to check the specific application of the PDF file. The steps are as follows:

(1) Open the file;

(2) Select the "File" menu in the menu bar;

(3) Select "Text Attributes"

(4) Select the "Description" command

(5) In the "PDF Information", you can see the creator information of the PDF file. If its creator is PDF Writer, customers can re-create PDF files through Distiller to meet prepress needs.

You can also change the PDF file's preflight settings via PDF Writer or other available settings.

4. Missing font

One of the problems with common PDFs is the loss of fonts. If there is no built-in font in the PDF, it will be replaced by Adobe Sans or Adobe Serif, and the desired visual effects cannot be obtained.

The reason why we couldn't embed a font in PDF is as follows:

(1) When Postscript was created, the font could not be activated in the local application;

(2) In Postscript settings, the font inclusion type is not set to "all";

(3) The settings of Distiller are incorrect;

Note: In Distiller a Postscript file, all fonts should also be embedded.

You can use PitStop Pro to solve the font loss problem:

(1) Select the "selec Object" tool;

(2) Select the Window command and then select Show Pit Stop Inspector

(3) Select the "Text" tab

(4) Click the "Font Picker" button

(5) Select the "Pages" tab. This will show the fonts used for a particular page. The "Documents" tab will show the fonts used for the entire file. The "System" tab will show the fonts installed by the system.

(6) Use the "System" tab to display the system-activated fonts, select the font you want to embed in the PDF, and then select the "Embed Font" check box

(7) Click "OK" to embed the font

5. Color separation

Color processing during printing separation has always been a difficult problem, especially in software that does not support CMYK four-color, spot colors and RGB files must be converted to the corresponding CMYK file.

If you use typography software for color separation, the color separation procedure should be used for the best color separation. Acrobat takes a step further in processing colors. Not only can it accomplish color conversion in the Advanced Print Setup dialog box, but it can also soft-dye colors through the monitor before printing. The steps are as follows:

(1). Select “Advanced” and then “Separation Preview”. The separation preview dialog will show the colors contained in the file. If the file contains a spot color, the color is displayed along with the CMYK color.

(2). When the cursor moves on the page, the ink percentage at the cursor position will appear on the information bar. At this time, you can select a specific color to modify and view the color mixture, which is very helpful for the four-color printing with a two-color printing machine.

6. Wrong color space

Another frequently encountered PDF file problem in printing applications is the presence of images and text in CMYK mode in PDF files. In PitStop Pro, to solve RGB image problems, the process is as follows:

(1) Find the "selec Objects" tool

(2) Select "Window" and select "Show Pit Stop Inspector"

(3) Select the "Color" tab

(4) Click the "Change into CMYK" button at the bottom of the dialog box. In PitStop Pro, the process for solving RGB problems is as follows:

(1) Use the "Secec Objects" tool to select some or all of the RGB text

(2) Select "Window" and select "Show Pit Stop Inspector"

(3) Select the "Color" tab to confirm the text color space

(4) Select "Window" and select "Show PitStop Global Change"

(5) Find the "Object" tab and select the "Color" tab

(6) Select the "RGB Range" button in the left column and specify the color gamut if required

(7) Click the "CMYK Range" button in the right column to describe the color to which the RGB text is converted.

(8) In the lower left corner of the "Overall Conversion" dialog box, indicate whether the conversion should be applied to the current page, a group of pages, or the entire file.

(9) Click Apply.