PDF: History, Features & Co.

While this is not a complete guide to PDFs, here you will find the major types of PDFs and their purposes

Like for any other graphics, a person using a PDF has to make sure he is using the right one for the job. Saying that a PDF “is good for printing” is like saying that “EPS files contain vector graphics”. Both statements are inaccurate and to a certain degree even untrue. PDF files serve many purposes—you cannot use a PDF which was intended for onscreen viewing also for offset printing, unless you want poor results. PDFs that were originally intended for offset printing, cannot be used for online viewing due to their size, the same way you wouldn’t use TIFF or EPS files for web design.

As this is about Desktop Publishing, I won’t delve into the settings to be used for PDFs intended for screen viewing. The focus of this article is on those types of PDFs which can and should be used for printing.

Many versions of the same file

As Adobe’s PDF technology advances, new and improved PDF versions make their appearance. Here is a list of the most recent PDF versions, what they support and what versions of Acrobat can be used to read or deal with them.

PDF 1.3
Supported by Acrobat 4 or later. It supports CMYK and spot colours, notes. Some security features are also supported. It does not support transparency. This PDF version is the most widely supported by printing firms.

PDF 1.4
Supported by Acrobat 5 or later. It supports all of the features of PDF 1.3, but it also supports transparency. The security features have been improved, compared to its predecessor. Support for JavaScript is also improved. When transparencies are present, some problems might arise when a PDF 1.4 is given to a printing firm. It depends on the printer’s RIP. Ask your printer if their RIP supports transparency and what PDF version they can handle.

PDF 1.5
Supported by Acrobat 6 or later. Compression techniques are improved. Media files such as movies and layers can be supported with this version.

PDF 1.6
Supported by Acrobat 7. 3D artwork can now be embedded. Amongst other things, it also has enhanced annotation and watermark features.

For those who want to know more about the development of this versatile file format, here is a very insteresting article by L. Leurs, entitled History of PDF.

PDF/X

PDF/X is a PDF’s subset. It is still a PDF, but the person making the PDF has to follow certain criteria in choosing the settings to produce the PDF/X. The purpose of the PDF/X is to resolve some of the most common problems that printing firms encounter when using PDFs provided by designers, such as RGB images, missing images and fonts and others. The PDF/X is therefore intended for printing purposes and not for online purposes. Also the PDF/X is not the best solution when you want to print documents from your desktop printer, as usually that type of printer gives better results with RGB images, while PDF/X has to be strictly CMYK (with allowance for spot colours, which anyway cannot be rendered correctly on an RGB desktop printer).

Because of its restrictions, PDF/X sacrifices flexibility for functionality. While you will hardly have any problems when printing a PDF/X, there are things you are not allowed to do and therefore your design might suffer.

There are several standards of PDF/X and the most used are PDF/X-1a and PDF/X-3.

PDF/X-1a

Making a PDF/X-1a isn’t actually that difficult. InDesign CS allows you to make one simply using its built-in Export PDF option. However for those who do not use that program, who want to make a preflight check before they make the PDF, or need to troubleshoot a PDF to make it PDF/X-1a compliant, it is important to know the requirements of the PDF/X-1a standard. These are the requirements for the PDF/X-1a:

• The PDF version has to be 1.3.
• The PDF has to be a composite and not colour separated.
• All fonts are embedded.
• All images are to be at their highest resolution and no OPI is permitted.
• LZW compression is not allowed. All other non-lossy compressions are allowed.
• JPEG is the only lossy compression allowed.
• Either Trim Box or Art Box have to be specified. The Art Box defines the extent of a pages’s meaningful content. If you are just using a portion of a page, the Art Box will be that area where text, pictures and needed white space are, while the rest of the page, which remains blank, isn’t considered. If you are using the whole page, then you need to specify the Trim Box. This page gives you a good idea of the different types boxes as intended in the PDF/X standard. Unless you are Italian you can’t read it, but there is an illustration about half way down the page which shows you the trim box, crop box, media box, etc.
• Media box has to be specified.
• Trapping has to be specified.
• The Output Intent is to be specified.
• The PDF can only be CMYK or contain spot colours. No RGB or LAB colour modes allowed.
• Bleed Box and Crop Box are optional.
• Anything that is not needed for printing, such as notes, forms, buttons, Javascript, comments and so on are not allowed.
• Transparency is not allowed. When making PDFs with InDesign, if you used drop shadows or transparencies of any type, make sure you set the PDF standard to PDF/X-1a. That should treat transparencies in a way that will not compromise your output. But if your PDFs don’t look like you expected and you have to provide PDF/X-1a to your printer, then you need to get rid of all the transparencies and drop shadows within InDesign.

PDF/X-3

PDF/X-3 allows you to do a few more things, but essentially the list of settings above applies to PDF/X-3 as well. The differences are:

• RGB is allowed, but only with a profile.
• LAB mode is allowed.
• Colour management for CMYK is allowed. While with the PDF/X-1a standard you have to specify a printing profile, with PDF/X-3 you don’t have to. You can simply say that the PDF will be CMYK and you can then use your own profile.