Preflighting is the process of checking if the digital data required
to print a job are all present and valid. Nowadays it is usually PDF
files that are sent to a printing company. The PDF file format is a
solid standard to exchange pages, ranging from single ads to complete
publications. Using PDF is however no guarantee that the receiver of a
file can actually output it as intended. To make sure that a file
matches the requirements to reproduce its correctly, it needs to be
checked or ‘preflighted’. Checking files is essentially done to avoid problems in processing or printing content.
These are the TOP 10 problems when using PDF in graphic arts. Don’t take my word for it, this list actually comes from Adobe.
- The resolution of images is too low.
- Fonts are not embedded in the PDF.
- The wrong color space is used.
- The information about trim or bleed are incorrect.
- There is an inconsistency with the native file.
The original page, as viewed in QuarkXPress or InDesign or whatever
other application looks different from the PDF. Hairlines might be
different or gradients have changed.
- A spot color is misnamed or it is accidentally converted to a process color.
- Images are compressed too much. This causes a quality loss and in some cases artifacts appear inside or around the images.
- The page size is incorrect.
- There are problems with transparent objects.
- ICC profiles are missing or incorrect.
One of the reasons why many of these problems go undetected is that
designers have the habit of making proofs from their lay-out, checking
those proofs and then creating PDF files. These PDF files don’t get
looked at, they are sent straight to the agency or printer. It would be
far better if designers created PDF files and then made a proof of these
files. This way the consistency between supplied file and proof is much
Who should preflight when?
The earlier in a process that problems are detected, the easier and
cheaper it is to fix them. This implies that designers should preflight
their creations before sending them to their agency or printer.
Printers or service bureaus should always preflight incoming data,
simply to make sure that the quality of the product that they will
deliver meets the customer’s demands.
It is worthwhile to know that there are two technologies available to
ensure that files only need to be preflighted once. These are Enfocus
‘Certified PDF’ and the Ghent Workgroup ‘Universal Proof of Preflight’.
Essentially both systems allow a preflight application to embed metadata
in a checked PDF to document how the file has been checked. The
receiver of such a file only needs to verify if this ‘seal’ is present.
In case you wonder: the term preflight was derived from the long list of
checks that pilots have to complete before taking off with an airplane