Create PDF/A Documents for Long-term Archiving
PDF/A – what is it?
PDF/A provides this security and liability.
But it is not only important for long-term archiving that PDF files always look the same. Even when a document is printed out on a system other than the author’s, the result may look different than “intended”. This is an effect that must be prevented.
PDF/A Conversion with SEAL Systems
What Advantages Does PDF/A Offer for Archiving?
"As Created, so Printed in 100 Years Again." – The ISO Standard Ensures Long-term Reproducibility.
PDF/A Can Accommodate a Wide Range of Other Formats.
PDF/A is Searchable by Text.
Additional Functions such as Indexing and Digital Signatures are Possible.
PDF/A is the First Preliminary Step to Automatic Readability (Tagged PDF).
PDF/A Now even Allows the Integration of 3D Content from the Engineering Environment.
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What is the Difference between PDF/A and Normal PDF?
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The European hospital center CHUV searched for a possibilitiy to convert all documents automatically according to ISO standard. 8000 employees from 92 nations care for more than 41,000 patients yearly. In this connection around 4,000 files must be handled with different formats like docx, html, rtl, and TIFF. With a conversion workflow and the DPF technology from SEAL Systems this challenge was solved without any problems.
FAQ on PDF/A Conversion
Why PDF/A was actually Created?
The ISO standard PDF/A-1 was published in 2005 with the aim of specifically narrowing the functional scope of PDF so that standard-compliant files are suitable for long-term archiving. At that time, PDF was still defined by the Adobe Reference. However, PDF/A was not intended to create a new PDF Reference. Instead, the existing PDF reference was “downsized”.
In 2011, the second part of the standard was published: PDF/A-2. The most important innovation was certainly the fact that this part of the standard could now be based on PDF as an ISO standard, ISO 32000-1 (corresponds to PDF 1.7). The implicit XMP definition from Adobe had also become an ISO standard in the meantime. The further development of the PDF format also allowed newer functions to be approved for PDF/A. These include, for example, OpenType fonts, JPEG2000 image compression, and newer comment types.
In 2013 the 3rd part of the standard appeared: PDF/A-3. The only innovation here is the possibility of embedding any files. All that needs to be done is to mark how the embedded files relate to the envelope PDF/A-3: Previous version or other representation.
What are the Main Characteristics of a PDF/A File?
Fonts: The most well-known feature in this context is probably the embedding of the fonts used. Every font used must also be embedded. If even the highest level a is to be achieved, each character must be marked with the corresponding Unicode name, even if no Unicode font is used at all.
Colors: Colors should also not be left to chance or to the preference of the printer used. There are generally valid color models – this has nothing to do with PDF. These color standards should be used. And if this is not possible, then you should specify in the PDF file on which device it should preferably be output. Then a conversion to a generally valid color model can be done later.
Encryption: PDF/A generally does not allow encryption. Also, in contrast to normal PDF, compression is not permitted throughout. Images can be compressed using a standardized process – such as Tiff, JPEG and, as of PDF/A-2, JPEG2000. More is not possible, because the contents of a PDF/A file should be accessible as easily as possible. The file must be protected against uncontrolled modification by a management system (DMS). In the case of document distribution, the use of digital rights management (DRM) is also an option. However, since this encrypts the files, a standardized PDF/A must still be kept on hand internally.
Digital signatures: Digital signatures can be used to prove that a PDF file has not been modified after a certain point in time. PDF/A-1 did not make any statements about digital signatures. As a result, they were automatically allowed. And since PDF inherently allows handy embedded signatures, this feature was also popular. But only PDF/A-2 includes the reference to signature standards, so that errors in the use of signatures for long-term archiving are excluded here.
Transparencies: In the original PDF reference, transparencies were described inaccurately. In the PDF ISO standard they are now so precise that they can also be used safely in long-term PDF. As of PDF/A-2, transparencies are therefore permitted. The ability to use transparencies is an important reason for switching to PDF/A-2 if you have previously created PDF/A-1.
Scaling options: PDF/A-1 had a size limitation of 200 inches = 5.08m because of the PDF 1.4 base. This was too small for many applications. Scaling during PDF/A generation was the work-around. However, the original size was then no longer known in the PDF/A file itself. With PDF/A-2, a standard built-in scaling factor can now be used, the so-called user units. This means that extensions of around 300 km are now possible.
Layers: In the past, the usability of layers in PDF/A was often missed. This PDF function is now also better standardized: a layer must be marked as a default layer. Then layers, which are helpful e.g. when converting from CAD models, can really be used.
Embedding files: An important innovation of PDF/A-2 was the ability to embed other files. If these files are themselves PDF/A compliant again, this feature can be used. With PDF/A-3 it is even possible to embed arbitrary files. However, PDF/A-3 in no way guarantees any quality of the embedded files. For this you have to impose regulations on yourself, so that you don’t end up with a wildly uncompromising PDF/A-3. However, there are numerous applications for the possibility of embedding arbitrary files in PDF/A-3:
- 2D PDF views of a construction with stored original 3D geometry
- Invoice as PDF and stored invoice data as XML (ZUGFeRD)
- Originally existing non-PDF/A file but with valid digital signature embedded in the derived PDF/A file.
Tagged files: Adobe has also created its own standard, the XMP standard, to mark files using XML tags. A file tagged in this way carries the information of what it is actually for within itself; a safeguard for the failure of the DMS system. XMP also includes several schemes for keywords. If the keywords you would like to use for your PDF/A archive are not included, simply create your own schema and embed it in the PDF/A file.
What's the Significance of PDF Levels?
PDF/A-1 is available with levels a and b. As of PDF/A-2, level u is also available.
Level b is the lowest, but already guarantees the clear visual reproducibility of the PDF. This level is usually sufficient. Often, no higher level can be achieved with the existing sources.
Level u additionally requires that all characters in the file also have their internal Unicode name. Note: if you need Unicode, you can do this with level b as well. He just has to use a Unicode font there.
Level a is the complete standard. Here, requirements for automatic searchability are added. Objects: like headlines, images, indexes must be marked as such. This is the first step towards PDF/UA.