PDF/A is an ISO-standardized version of the PDF (Portable Document Format) specialized for the digital preservation of electronic documents.
PDF/A standard is designed to use the PDF format for archiving documents. This means that the compliant documents should contain all the information necessary for displaying the document embedded in the file. This includes all content, fonts, and color information. A PDF/A document is not permitted to rely on information from external sources. Other key elements to PDF/A conformance include:
- Audio and video content is forbidden.
- JS and executable file launches are forbidden.
- All fonts must be embedded. This applies to the Standard 14 fonts as well.
- Color spaces should be specified in a device-independent manner.
- Encryption is forbidden.
- Use of standards-based metadata.
- Transparent objects and layers are forbidden.
- LZW and JPEG2000 image compression models are forbidden.
There are three major versions of the standard – PDF/A-1 (2005), PDF/A-2 (2011), PDF/A-3 (2013).
PDF/A-1 standard uses the PDF Reference 1.4 and specifies two levels of compliance.
Its goal is to ensure reliable reproduction of the visual appearance of the document.
Its objective is to ensure that documents content can be searched and re-purposed. This compliance level has some additional requirements:
- Document structure must be included.
- Tagged PDF.
- Unicode character maps
- Language specification.
RadPdfProcessing does not support PDF/A-1a level of compliance.
Pdf/A-2 standard uses the PDF Reference 1.7. In addition, it has the following features:
- Support for JPEG2000 image compression.
- Support for transparency effects and layers.
It defines three conformance levels.
Corresponding to the PDF/A-1a
RadPdfProcessing does not support PDF/A-2a level of compliance.
This level corresponds to the PDF/A-1b.
Similar to PDF/A-2b level with the additional requirement that all text in the document has Unicode mapping.
PDF/A-3 differs from PDF/A-2 in only one regard – it allows embedding of arbitrary file formats into the PDF file.
This conformance level requires character mapping to Unicode and it doesn't require embedded logical structure (like structure tree and tags).
The PdfFormatProvider class allows to export a RadFixedDocument to PDF and specify some specific settings when doing so. More information about the available export settings can be found in the Settings article.
To comply with one of the versions of the standard, you need to specify ComplianceLevel different from None. The snippet in Example 1 shows how this can be achieved.
Example 1: Export PDF/A compliant document
PdfFormatProvider provider = new PdfFormatProvider(); PdfExportSettings settings = new PdfExportSettings(); settings.ComplianceLevel = PdfComplianceLevel.PdfA2B; provider.ExportSettings = settings; return provider.Export(document);
PDF/A standard requires documents to contain all fonts used in them. RadPdfProcessing does not support embedding of the standard 14 fonts used in PDF documents, so using them will prevent the document from complying with the standard. More information about font embedding is available in the Fonts article.