Export to PDF/A Format

PDF export functionality supports creating archive PDF documents (PDF/A).

PDF/A is a specific version of the PDF format for long-term archival preservation of electronic documents. This format differs from common PDF format by excluding all features that can be dangerous for long-term document storage (for example font linking, encryption, etc.).

PDF/A format is standardized by ISO. ISO requirements for viewer applications contain color management guidelines, embedded fonts support, and a user interface for reading embedded annotations.

There are several versions of PDF/A format:

PDF/A-1 — See Part 1: Use of PDF 1.4 of the ISO PDF/A standard.
PDF/A-2 — See Part 2: Use of ISO 32000-1 of the ISO PDF/A standard.
PDF/A-3 — See Part 3: Use of ISO 32000-1 with Support for Embedded Files of the ISO PDF/A standard.

The difference between PDF/A-2 and PDF/A-3 is insignificant for CAD applications, therefore ODA Platform supports only PDF/A-1 and PDF/A-2 versions.

To specify a version of PDF/A format, the PDF_A_mode enumeration from the PDFExportParams class is used.

Note: When exporting drawings into archive PDF format, it is strongly recommended to use the PDF/A-2 version for the following reasons:

PDF/A-1 version does not support layers.
PDF/A-1 version does not support transparency and the MergeControl parameter is always set to the LinesOverwrite value.
Values of real data type (for example, coordinates) cannot be greater than 32767; therefore, in some cases DPI resolution should be reduced.
Strings (including streams and stream parts) cannot have a size greater than 64 Kb. This leads to the following disadvantages:
1. Picture quality is set to the minimum value.
2. ASCII hex encoding is unavailable.
3. Flat encoding is enabled to reduce the possibility of issues during the export process.
PDF/A-1 version does not support the measuring feature.

To export to the desired version of PDF/A format, use the setArchived() method of the PDFExportParams class. To retrieve whether exporting to the archive PDF format is enabled, and if enabled, which version of PDF/A format is used, call the archived() method of the PDFExportParams class.

There are several restrictions and disadvantages of using the PDF archive format for export:

The ODA Platform does not support TrueType font optimization yet, therefore the TrueType font optimization flag is switched off if PDF/A support is applied.
According to ISO standards, the PDF/A format is not compatible with the PRC format. Therefore, if both modes (PRC and PDF/A support) are switched on, an error occurs. See Export to PDF using PRC for details about exporting to a PDF file with PRC support.
Fonts can only be embedded in a PDF/A document and this leads to an increased document size.

See Also