General questions on PDF/A

(Source: PDFA Competence Center)

If I have PDF/A, do I no longer need paper copies?
This is a primary goal of PDF/A. Digital documents should remain in electronic format, giving the user a wide range of additional features, e.g. like full-text searching instead of manually looking through paper dossiers or file cards.

Up to now we've used "normal" PDF for archiving digital documents. Is this not sufficient? Why is PDF/A better?
PDF/A is a subset of PDF that eliminates certain risks threatening the one-to-one future reproducibility of the content. PDF/A forbids dynamic content to ensure that the user sees the exact same content both today and for years to come. Everything that is required to render the document the exact same way, every time, is contained in the PDF/A file: fonts, colour profiles, images etc. PDF/A is also an ISO standard, guaranteeing that future software generations will know how to open and render PDF/A files.

How does PDF/A compare to ODF (Open Document Format)?
Open Document Format is a file format for office use, based on XML. ODF has some of the good properties also found in PDF/A: the specification is publicly available, it is an international standard (ISO/IEC 26300:2006). However, ODF is not self contained and (currently) nowhere nears as widely distributed as PDF.

How does PDF/A fare with respect to corruption?
PDF/A fares just as well as any other file format. More commonly, the data medium itself (CD-ROM, hard disk, etc.) is the reason that files cannot be read, and not the file format.

Are PowerPoint files good candidates for converting to PDF/A?
Yes. You might however have to take into consideration certain preparatory steps, for example ensuring that annotations are also carried over into the PDF/A file.

Can PDF/A files contain copyright information, like TIFF can?
Yes. PDF/A gives you the possibility to save various different metadata (for example the copyright) in the document. Extensible Metadata Platform (XMP), a technology that unifies different metadata methods, is used for the metadata in a PDF/A file.

Will future developments to the PDF/A standard make current PDF/A versions obsolete?
The ISO standard requires that future PDF viewing applications must be backward compatible, so that they are capable of correctly displaying older versions of PDF/A.

How can you best make PDF/A files text searchable?
If a PDF/A file is created from a digital text document, the text will automatically be recognized. Normally you don’t have to worry about a PDF/A file being text searchable, unless the file was created from a scanned paper document or image. But even then, OCR can be used to make it searchable. In this case, however, only PDF/A-1b is possible and not the more stringent PDF/A-1a.

Since PDF/A-1a lays especially high requirements on the fonts used and on the file structure, this level of conformance is recommended over PDF/A-1b for an exact text searchability, text extraction, and for the reuse of content. PDF/A-1b supports text search, may however not find all instances of a text if there are anomalies with character coding.

How are (hypertext) links dealt with in PDF/A?
It should be ensured that the links in a document are still legible, even if they don’t point to an active destination.

What about "mixed" objects in PDF, like audio and video. Can these be used in PDF/A?
PDF files with dynamic objects like audio and video cannot be converted to PDF/A. PDF/A must guarantee an exact reproducibility, which is not possible with embedded objects like sound or movies. These types of objects usually require an external player (and quite often in a specific version). There is no guarantee that the player application will be available in the future.

How is PDF/A on memory space? Are PDF/A files much larger than normal PDFs?
A PDF/A file might be marginally larger than the original PDF file it was created from (provided they don’t use different image resolutions or compression methods). Fonts are embedded in a PDF/A file (which is often also the case in “normal” PDF files) and more information is stored in the metadata. Some colour profiles could, in certain cases, lead to a much larger file size, but this is rare and is highly dependent on the particular case.

Can PDF/A be used with CAD?
CAD drawings (Computer Aided Design) are electronic technical drawings that can be produced by several different software applications, each using it’s own proprietary file format. The long-term archiving of CAD documents can cause difficulties due to the native electronic formats. PDF/A is therefore very suitable for archiving CAD drawings, unless the drawings contain 3-D objects (which are not permitted in PDF/A). In this case, a possible solution is the PDF/E standard (”E” for “Engineering”).

Is compression allowed in PDF/A?
Yes. ZIP file compression is permitted, and images can be compressed using JPEG compression. LZW compression is, however, forbidden.

Can PDF/A files be encrypted?
No. Encryption is not permitted in PDF/A files. If, for example, a file requires a password to open it, then either a person who knows the password or a digital key must be available. The content of a PDF/A file must however always be accessible, which is why encryption is not allowed. A possible way to protect sensitive data in a PDF/A file is to put access constraints on the storage medium where the file is located (e.g. password access to the folder).

Do PDF files from Acrobat 8/9/X, that were saved as 1.7 files, lose any properties when they're converted to PDF/A?
This is quite possible. PDF/A is based on PDF 1.4. If the PDF file is using features that were first introduced with PDF 1.5, 1.6 or 1.7, these could be lost with the conversion to PDF/A.

Can bookmarks in a PDF file cause problems in PDF/A?
No. Bookmarks are permitted in PDF/A.

Can PDF/A documents be made "accessible"? We want to create documents that can be read by a screen reader.
Accessibility and PDF/A go hand-in-hand. Since both PDF/A-1a and “accessible PDF” files have special requirements for the file structure and on the fonts used, it is relatively unproblematic to create accessible PDF files that also conform to the PDF/A standard.

Can annotations and notes be used in PDF/A files?
Most forms of comments (annotations and notes) are permitted. There are however certain requirements, for example the comments must be visible, and they cannot be of the type “sound” or an attached file. Some types of comments that were introduced after PDF 1.4 (the basis for PDF/A) are not permitted, for example Polygon tool.