PDF Verification Guide

Verification of the completed PDF files has a particularly important role in the process of submitting materials to be printed. Since printing houses typically use software based methods to verify incoming materials, such verification focuses first and foremost on the technological aspects. It is a difficult task, because automated verification programs can sometimes produce misleading results due to the structure of the PDF file, since each job is different and the internal structure of the PDF files can also vary to a great extent.

Notwithstanding these difficulties, due to the forced acceleration of production processes, software based automated verification and error-correction solutions have an increasingly important role as they can greatly facilitate the detection of frequently encountered file errors. The solution for this problem is Adobe Acrobat Professional, which is commonly used by customers (Adobe Reader is not suitable for print production checks!) The ‘View > Tools > Print Production’ of the application includes the tools that can help you check and correct PDF files created for printing.

Preflight tools
1: Preflight
Software based checks using profiles.

 

2: Output Preview
A tool for visual verification.

 

 

 

 

 

 


Preflight checks

You can automatically check the finished PDF files with the Preflight module of Acrobat (not included in Acrobat Reader), using various pre-configured sets of criteria (preflight profiles). This interface can be used to run pre-installed profiles that check the properties of the PDF file (and its objects) against pre-configured criteria. After running a profile, you will get a list of result from which you can determine which PDF parameters deviate from those configured in the profile. As the properties of the PDF document depend on the parameters of the finished printed product (number of colors, paper type, printing technology), there are multiple profiles from which you can always select the one that is the most suitable for the parameters of the given product.

Preflight profils1: Imported Profiles
Since verification criteria and checks can be customized in Preflight profiles, you can also create your own unique profiles, or import profiles created by other users. The Imported profiles section includes profiles imported from these external sources (compatibility between program versions is an important consideration). If you have no experience in creating profiles, then we recommend downloading and importing the Pauker Preflight Profile that we created.

2: Prepress Profiles
Here you can find standard preflight profiles made for various printing technologies and according to various standards. Profiles marked with an active wrench icon can automatically fix certain errors (found in the PDF document).

3: Analyze
Pressing this button will start the analysis according to the selected profile. Profiles that provide fixups will only perform an analysis  if you press the ‘Analyze‘ button, however, if the ‘Analyze and fix‘ button is used, the PDF file will be automatically corrected according to the pre-configured settings.

 

 

Downloadable Pauker Preflight Profile

 

 

The Preflight results are always presented as a list which contains the severity of the detected non-conformity (error, warning, information). It can also display the objects with errors, highlighting them in the analysed PDF file. There are requirements that a print-ready PDF file must meet, while other conditions are only checked to facilitate the printing of the document, and to improve the aesthetic qualities of the final product. It is particularly important to emphasize, however, that software based checked cannot fully replace visual checks and human verification as the complexity of the PDF files and the wide variety of printed products, it is difficult to create a perfect Preflight profile. Also, there are special technological conditions that are difficult or impossible to check in this way. For this reason, even if the given Preflight profiles have found no errors in a given PDF file, it does not necessarily mean that the PDF file in question is flawless, and does not contain any file errors!

 


Visual checks (Output Preview)

Another important tool for checking PDF files is the Output Preview feature, because it can be used, in addition to the Preflight checks, to examine the completed PDF file if the correct color values have been used.

 

CMM and Preflight overprint preview1: Simulate
Settings controlling the simulation of how colors will look when printed. For detailed, please refer to Use of color management.

2: Show
You restrict Acrobat to display only objects with the properties you select here (only images, only text, only CMYK with ICC profile, etc.). It is extremely useful in filtering out certain elements with “faulty” properties.

3: Separations
You can use this option to enable and disable color plates one by one in the file. Certain frequent color separation related errors can be easily spotted with this feature. For example, you can look for black text sections or die lines not set to ‘overprint’, or non-separated spot colors.

4: Total Area Coverage (TAC)
This value shows the total coverage of color separations at a given point. This value is important, since, for example, in the case of offset printing, surfaces with a total coverage of 300% (TAC) may lead to set-off or drying problems after printing.

5: Total Area Coverage (TAC)
This value is also useful for checking the total coverage, but it does not show the TAC value of a point, but rather it characterizes the surface of an entire page. Areas with a TAC value greater than the percentage entered as ‘Limit’ are shown in green highlight color. It is advisable to keep the total area coverage below 280% for sheet-fed offset printing, if possible.