PDF = Portable Document Format
PDF stands for Portable Document Format, standardised by Adobe in 1993. PDF was developed with the aim of creating lighter documents.
PostScript was used to drive the RIPs of film imagesetters. These files were so heavy and unreadable that no one knew what was happening. There was a need to develop a more compact file — in the language of high-end imagesetters and printers — that you could actually view on your screen. All objects, text, vectors and images had to remain 100% intact and be of high resolution.
Besides plain text and images, PDF files can contain a variety of content: logical structuring elements, interactive elements such as notes and forms, layers, rich media (including video), three-dimensional objects and various other data formats. The PDF specification also provides for encryption and digital signatures, file attachments and metadata to enable workflows that require these features.
GrafiStore has worked with PDF since its earliest development. Do you have questions about PDF? Then come to us.
The technical approach to PDF
A PDF file is often a combination of vector images, text and bitmap images. The basic content types in a PDF are:
Text, stored as content streams (so not as plain text);
Vector images for illustrations and designs made up of shapes and lines;
Raster images for photos and other types of images;
Multimedia objects in the document.
In later PDF revisions, a PDF document can also support links (within a document or to a web page), forms, JavaScript (initially available as a plugin for Acrobat 3.0) or other types of embedded content that can be processed with plug-ins.
PDF combines three technologies
A subset of the PostScript programming language for page description, to generate the layout and graphics.
A font-embedding system so that fonts travel with the documents.
A structured storage system to bundle these elements and all associated content into a single file, with data compression where needed.
Why we pre-flight PDF files
Pre-flighting is file checking done in advance to prevent problems during processing or printing. The most common problems can easily be prevented by pre-flighting every file. In 2017 the Ghent Workgroup conducted a survey among 1,100 companies, with the following findings. The percentage is shown next to each common error.
Resolution too low (70%)
Incorrect colour space (50%)
Missing bleed (50%)
Fonts not embedded (40%)
Transparency issues (30%)
Incorrect number of spot colours (30%)
Incorrectly applied overprint (30%)
Ink coverage too high (30%)
Incorrect colour profiles (30%)
Wrong dimensions (30%)
Incorrectly flattened transparency (30%)
Colour inconsistency (20%+)
Wrong output intent (20%)
Spot colours incorrectly converted to CMYK (20%)
Incorrect technical info for cutting and spot colours (20%)
To a lesser extent there are also problems with corrupt fonts, corrupt PDF files, incorrect CMYK separations, missing objects, RIP errors and incorrect use of layers.
"Imagine misprinting just one file. How much does that cost?"
There is much more to tell about PDF; the story certainly does not end here. The bottom line is that printers and service bureaus should always pre-flight incoming PDF files — simply to be sure that the quality of the product they deliver meets the customer's requirements.
There are two software developers we trust in this process:
Enfocus (Connect YOU, PitStop Pro, PitStop Server)
Callas (pdfToolbox, pdfToolbox Server)
GrafiStore has known these processes for more than 25 years and builds custom PDF-checking solutions suited to your processes. Because there is no single solution that works for everyone, we always look at the business processes, equipment, software and wishes. That is what we are here for.
Get in touch with GrafiStore.
