Non Standard Annotation Objects

[JustADetailer]

I'm working on a project for a software called Bluebeam Revu. It allows you to add all kinds of data to markups based on a definition that's also included as an object in the pdf.

For Example:

The Object:

5 0 obj<</Type/Annot/Subtype/Line/L[1080 612 1512 612]/BS<</Type/Border/W 1/S/S>>/C[0 0 1]/P 4 0 R/F 4/Rect[1074.5 606.5 1517.5 617.5]/AP<</N 6 0 R>>/NM(fitz-A0)/IC[1 1 0]/Subj(Beam)/BSIColumnData[()()()()()(1)()()()()()()()(Galvanized)()(No)()(0)(No)()]/M(D:20230927160613-04'00')/SlopeType 0/PitchRun 12>>
endobj

The Definition of all of the fields contained in the /BSIColumnData

29 0 obj[<</Subtype/Text/Name(Description)/DisplayOrder 0/Multiline false>><</Subtype/Number/Name(WeightFt)/DisplayOrder 1/Format/Normal/Precision 2>><</Subtype/Formula/Name(WeightTotal)/DisplayOrder 6/Format/Normal/Precision 2/Expression([Length] * [WeightData] * [Quantity])>><</Subtype/Choice/Name(Size)/DisplayOrder 2/Format/Normal/Precision 2/Items 33 0 R/DefaultValues[]/AllowCustom false>><</Subtype/Formula/Name(WeightData)/DisplayOrder 3/Format/Normal/Precision 2/Totals false/Expression([Size])>><</Subtype/Number/Name(Quantity)/DisplayOrder 4/DefaultValue(1)/Format/Normal/Precision 0>><</Subtype/Number/Name(Cost)/DisplayOrder 5/Format/Normal/Precision 2>><</Subtype/Number/Name(Copes)/DisplayOrder -1/Deleted true/Format/Normal/Precision 0>><</Subtype/Number/Name(Moment Connections)/DisplayOrder -1/Deleted true/Format/Normal/Precision 0>><</Subtype/Number/Name(Additional Shop Hours)/DisplayOrder 7/Format/Normal/Precision 2>><</Subtype/Number/Name(Plate Thickness)/DisplayOrder 8/Format/Normal/Precision 4/Totals false>><</Subtype/Number/Name(Plate Width)/DisplayOrder 9/Format/Normal/Precision 2>><</Subtype/Number/Name(Plate Length)/DisplayOrder 10/Format/Normal/Precision 2>><</Subtype/Choice/Name(Finish)/DisplayOrder 11/Format/Normal/Precision 2/Items 32 0 R/DefaultValues[]/AllowCustom false>><</Subtype/Formula/Name(Plate Weight)/DisplayOrder 12/Format/Normal/Precision 2/Expression([Plate Length] * [Plate Thickness] * [Plate Width] * 490 / 1728 * [Length])>><</Subtype/Choice/Name(IsPlatebyLength)/DisplayOrder 13/DefaultValue(No)/Format/Normal/Precision 2/Items 31 0 R/DefaultValues[1]/AllowCustom false>><</Subtype/Formula/Name(Weight of Plate By Length)/DisplayOrder 14/Format/Normal/Precision 2/Expression([Plate Thickness] * [Plate Width] / 144 * [IsPlatebyLength] * [Quantity] * [Length] * 490)>><</Subtype/Number/Name(Spacing)/DisplayOrder 15/DefaultValue(0)/Format/Normal/Precision 0>><</Subtype/Choice/Name(Is Spaced Item)/DisplayOrder 16/DefaultValue(No)/Format/Normal/Precision 2/Items 30 0 R/DefaultValues[1]/AllowCustom false>><</Subtype/Formula/Name(Spaced Item Quantity)/DisplayOrder 17/Format/Normal/Precision 2/Expression([Length] * 12 / [Spacing] * [Is Spaced Item])>>]
endobj

Question 1: What is the name of this extended data in the context of a PDF?

Question 2: Is there guidance somewhere for reading and or writing to this data?

Question 3: Can I create and attach my own data in a similar fashion?

Question 4: Completely unrelated. I've looked around everywhere on how to find the rotation of a 'word' or 'block' within a vector pdf but haven't found a solution. Has anybody found one?

[pubpub-zz]

Q1:
I've searched PDF 1.7 and 2.0 reference for this field without success. I think this is a private datafield that can be analysed only by specific viewers.
Q2:
pypdf accepts any fields : you can access them like any other ones.
Q3:
You should have a look at Pdf 1.7 reference, appendix E
Q4:
you have to use use Tm Matrix . you should also save context before and restore it after (q/Q)