10 Simple Things You Should Keep in Mind
most common problems in print that you can prevent by preflighting your PDF files.
- Check the resolution of images in your file.
For print output, the image resolution needs to be higher than for viewing a PDF on a screen. A general rule of thumb is the resolution should be 2X your halftone screen ruling. Otherwise you will see jagged edges and artifacts in the image.
- Check PDF files for RGB images and even converts them to CMYK
Unintended RGB images in PDF files can cause unexpected results after processing. The images could be of low quality, a final printed color could be incorrect, and there may even be an overall color shift.
- Check on presence, number and suffix of spot colors.
Most designers like to work with spot colors (e.g. Pantone), especially in logos. But in many cases, these logos need to be printed using only CMYK inks, as an extra 'dedicated' ink for the spot color is more expensive.
- Check font embedding, font size, font type and number of separations in combination with font size.
Numerous problems can occur with fonts. E.g. if a font is not embedded, the output equipment will need to replace that font with another font. This font might look similar, or not. In all cases it will be a different font. Small type can become hard to read when printed, especially if it's printed in multiple colors.
- Check for too high Rich Black color values
How do you define a nice deep ('rich') black, one that won't cause trouble on a printing press? Every company has their own recipe for a nice black. But a black that carries too much ink can be a problem for some printing methods. A black that's too heavy can cause web breaks on a web press and marking or set off.
- Check if white elements are set to knock out.
Ever seen a job where a white element that looks great on the screen or paper proof suddenly disappears when on press? White elements might be set to "overprint", which means that the white ink will be output on top of the inks below and basically disappear. Unless you are in packaging or use a specific white ink in your production process, the white elements should be set to "knock out".
- Check files for transparency.
Although transparency is now a widely accepted functionality within most design and page layout applications many printing companies are still wary of PDF files containing transparency and like to give them specific attention to ensure they are processed and imaged correctly.
- Check if hidden layers are present in the file.
Layers were introduced with PDF version 1.5. These layers can be visible, or hidden. If your proofer or your RIP doesn't support PDF v1.5 or higher and there are layers in the PDF, they will be placed on top of each other. If a file contains a hidden layer, which is set to 'Always print', it will be printed.
- Check if bleed is present in a PDF file.
If a file that contains images or content that extend to the edge of the page and it contains no or not enough bleed, white borders can appear after cutting the sheets.