Thought all PDFs were created equal?
PDF is the preferred format for supplying artwork for print, archiving, portable use and many other purposes. It is designed to make documents readable by everyone equally, regardless of operating system, hardware or the software used. However, certain considerations and standards must be observed if the file is to be used for print.
What is PDF?
PDF stands for Portable Document Format and has been in use for 20 years, ever since it was decided that there was a requirement for an encapsulated format which included the layout, colour, font and other information necessary to display a file in the same way anywhere.
The software used to view PDFs is called Acrobat and is developed by Adobe. The free version is called Acrobat Reader and is available from Adobe’s website. Acrobat Pro is used by print and other industries and gives more control over content and ‘preflight’ of PDFs.
PDFs can be simple print layouts or they can contain interactivity, video or forms. They can contain both raster (pixel-based) or vector content and can be used to save a photo or a vector logo equally well.
Saving as PDF
The method for saving a file as a PDF depends on the software and operating system used. If Acrobat (Reader or Pro) has been installed, most programmes should be able to output to PDF. Many programmes (especially design software) have the capability built in.
There are usually two options for saving as PDF: the obvious ‘Save As…’ and the less obvious ‘printing’ as PDF. In the second option, Acrobat sets up PDF as a sort of virtual printer, allowing you to create a PDF from the print dialogue.
The best way is to look in the menu of the software you are using to see if options for PDF exist. It may be under ‘Save As…’, ‘Export’, or there may simply be an Acrobat symbol:
- Look for ‘Save As…’ and select PDF, or
- Look for ‘Export’ and select PDF, or
- Go to Print dialogue (CTRL+P) and change the printer to ‘PDF’
The PDF format can be tailored to the intended use. Security settings can be applied or images can be reduced in resolution and quality for screen viewing, fonts can be embedded and printers’ marks can be added.
To keep things simple, there are certain presets usually built into the PDF dialogue. For example, ‘High Quality Print’ is suitable for home or office printing, whereas ‘Press Quality’ is better for high-end, professional printing; ‘Smallest File Size’ is best suited for files which are to be emailed or viewed online. All of these settings maintain transparency and the first two settings maintain spot colours if they are used; the last setting converts the colours to RGB.
With specialist software, such as the Adobe Creative Suite, there are industry-standard settings for supplying files for print. The two important ones are PDF/X-1a:2001 and PDF/X-3:2002. We’ll call these PDFX1 and PDFX3 for brevity.
PDFX1 is best suited to lithographic printing as it converts all colours to CMYK and flattens all transparency. PDFX3 also flattens transparency but it allows other colour spaces such as RGB and colour management systems, as they are then dealt with by the digital printing software. Both PDFX standards allow spot colours: in litho they are created as plates alongside C, M, Y and K; in digital printing they are dealt with as any other colour. However, it is best to convert spots to process for digital printing, to be sure of the colour change. This is done in the ‘Output’ menu under ‘Ink Manager’.
The de facto standard for print resolution has long been 300dpi, as this is the resolution at which the human eye cannot resolve two point and therefore sees images sharply. However, with improvements in print technology, graphics are often printed at 600dpi and give a sharp image even when viewed close-up. 300dpi can be used to reduce the size of the file. Note that the resolution of the final PDF is dependent upon the individual images used. The 600dpi setting will not increase the resolution of a 72dpi image, it simply limits the maximum resolution to save unnecessary file-size.
Marks and Bleed
The important point here is to include bleed in your document if any artwork goes off the edge of the printed area. This allows the printer to print this extra artwork and then trim into it, so that there is no risk of a white border round the artwork. Your document should be set up to include around 3mm of bleed. This is not possible in some software, such as Photoshop (because it’s not a design or layout programme) so allow an extra 3mm on every side and inform the printer that you have done this.
The ‘Ink Manager’ allow you to view the CMYK plates and any spot colour plates used in the design. This is important in litho printing because a plate will be created for each colour here and you will be charged accordingly. In digital printing this is not a problem but you should convert the spots to process so you can see any changes in the colour.
This is where you can apply transparency-flatting settings. For the most part, this can be left alone, but if you have used transparency in your design (drop-shadows, translucent graphics, etc.), we find that the safest setting for this is ‘Medium Resolution’. Don’t be concerned about the term ‘resolution’ here, your graphics will still be sharp.
There are, of course, other settings and options, but these are the primary settings you need to get your file to print as you want it to. At FirstpointPrint we can give you the advice you need or we can create the PDF for you from your original artwork.