Augmented PDF (embedded auras)¶
This document describes the format of Augmented PDF files, which are standards-compliant PDF files containing additional data allowing the display of Argo assets as an overlay when opened with the ARGOflow reader.
Thus these files can be opened in any PDF reader and the underlying document will be displayed. They can also be opened in the ARGOflow reader, and an extra interactive layer will become visible.
To allow standards compliance and integration with existing PDF production chains, the additional data is stored using standard PDF object types such as streams, dictionaries etc...
The assets follow the aura format as described in 
All ARGO-specific data is in a PDF dictionary with name
ARGO in the standard PDF Catalog dictionary, with the following properties:
Inside this dictionary is an PDF array with name
Auras: it is an array of references to PDF streams, one for each page of the PDF document, in order.
So for each page there is a PDF stream the with the following properties:
The content of each stream is a string representing a JSON array of assets in the Argo aura format 
Example of Augmented PDF structure as viewed in RUPS:¶
- RUPS (PDF visualization tool) from the iText project: https://github.com/itext/i7j-rups
- the official PDF format reference: https://opensource.adobe.com/dc-acrobat-sdk-docs/standards/pdfstandards/pdf/PDF32000_2008.pdf
- a shorter complete introduction: https://resources.infosecinstitute.com/topic/pdf-file-format-basic-structure/
- the ARGO aura format reference