With Adobe Reader software being freely available for every computer, portable document format (PDF) files have become the universal file format for electronically distributing, viewing and printing all types of data and information.
However, not all PDF files are the same, especially when it comes to printing. Adobe Acrobat software and PDF files have been around since 1993, and over the years, Adobe has created many versions of its Acrobat software, adding new features and expanding the functionality in many directions, says Prakash Naidoo, product manager and marketing manager of the wide format printing systems division of Oc'e South Africa.
PDF files can contain text, drawings, video, 3D models, scans, full-colour graphics, photos and hyperlinks. The idea behind this software and the PDF was to create a file format that could accurately represent documents independent of the application software, operating system and hardware that was used to create them, and of the output devices that are used to display or print them.
A properly created PDF file should contain all the information required to view the document on any computer or to print the document to any printer. However, this is not always the case, and many users experience PDF printing problems, the most common of which are transparency, fonts, page boxes and colour.
1. Transparency
The use of layers and transparencies in PDF files is the most common issue that affects processing speed and causes unexpected print results. Transparency defines what happens when two or more objects overlap each other in a document. Transparency features are used extensively in Adobe Creative Suite applications to apply special effects to objects, such as drop shadows, opacity and feathering.
Understanding transparency issues requires an understanding of the flattening concept. During the processing of a PDF file for printing, the first thing that occurs is the 'flattening' of the document.
Flattening takes all the layered, transparent objects on the page and converts them into opaque objects that look the same as the original transparent objects when printed. This flattening process can be quite time-consuming depending on the complexity of the PDF file. Usually, long processing time is due to hundreds or even thousands of transparencies needing to be flattened. Sometimes the transparent objects are not flattened correctly and the resulting prints do not match the original document.
2. Fonts
Another common problem is missing fonts in PDF files. The fonts used in the original document should be included in the PDF file created from it. Sometimes the fonts are not included, something that results in font substitution when printing.
3. Page boxes
Page boxes define the physical dimensions or size of the PDF file. There are five types of page boxes (MediaBox, BleedBox, CropBox, TrimBox and ArtBox) that can be defined in PDF that describe its size. A PDF file may not print correctly or take a long time to process if these are not defined properly.
4. Colour
Most engineering and architectural drawings are created in colour, even though they will be printed in black and white. It might be something as simple as colour lines or a company logo, or there could be more complex colour 3D models or high resolution photos. This colour information makes its way into the PDF files.
While more and more documents are being printed in colour, many are still printed in black and white. There can be issues when colour is converted to greyscale. For example, the colour yellow might be very visible on a monitor, but will become a very faint grey when printed in black and white. For on-screen viewing, RGB (red, green, and blue) colour is appropriate. However, colour printers use CMYK (cyan, magenta, yellow, and black) inks or toners. Colours can change during this conversion process. The absence or presence of colour in a PDF and how the colour is defined can impact processing times and the final printed output.
PDF printing methods
In order to understand how to solve these issues, it is important to know about the two methods that can be used to print PDF files. The first is the application/printer driver method. As its name implies, the application/printer driver method requires two pieces of software in order to print a PDF file. The application is software that can open and view the PDF file (such as Adobe Acrobat or Adobe Reader), while the printer driver is software used by the application to convert documents into a format that can be printed. Both the application and a printer driver are required to print the document. The disadvantage to this method is there is no easy way to handle batch printing of multiple PDF files. But, it is a good fallback when other printing methods fail.
The second method is direct PDF printing. This method uses an application to submit PDF files directly to the printer. The PDF file is converted within the printer using an Adobe PostScript interpreter or processor and no printer driver is required; however, not all printers support this method. The major advantage to the direct PDF printing method is its ability to batch print multiple PDF files in one job.
PDF printing solutions
Given these PDF printing challenges, there are two commonly applied solutions:
1. Preflighting
Preflighting or previewing PDF files in Adobe Acrobat software should alert you to potential issues before actually printing the documents. In many cases, the problems can even be corrected. Both Adobe Acrobat 8.0 Professional and Adobe Acrobat 9 Pro software have preflighting tools available to detect and correct common errors. While using Adobe Acrobat software can fix the majority of PDF issues, it cannot fix every problem. If the issues cannot be corrected, the software tools should alert you to potential trouble. At the very least, you'll know there is a problem before printing and distributing documents.
2. PDF/X
One of the easiest ways to avoid a large majority of PDF printing problems is to use the PDF/X standard. PDF files can be easily created in or converted to the PDF/X standard using Adobe Acrobat software and many other third party applications. The PDF/X standard is supported by Adobe PostScript 3 software and most third party processing software when using the direct PDF printing method. It was designed for the exchange of print-ready pages in the graphic arts and prepress world. PDF/X-1a and PDF/X-3 are two versions of this standard. Either one should work well, but it is better to use PDF/X-3 whenever possible.
The PDF/X standard requires that all fonts be embedded, appropriate PDF bounding boxes be specified, colour be correctly defined, and it eliminates transparency issues. Using PDF/X eradicates the most common errors in file preparation such as missing fonts, colour space issues, missing images, page box problems, and overprinting and trapping issues.
The result is that the PDF/X file generally processes faster than PDF files that contain transparencies and such files generally have less printing issues. The one disadvantage is that the file size can sometimes be larger than other PDF versions. When problems occur during the printing of a PDF file, the first course of action should be to convert it to PDF/X-3.
The PDF/X standard can also be set as a default for creating PDF files in Adobe products and other PDF generators. Standardising on PDF/X may provide more consistent and reliable output with your printer or software.
It's clear that printing PDF files is not as easy as clicking File>Print with your mouse. However, understanding the printing issues and options available will provide you with some great tools to be on your way to successfully printing PDF files.
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