I had this question come in today from Finland - they had a PDF that they imported, Scaled etc and then extracted the Vector Data from the PDF - they found that there was additional data in the extracted vectors than was shown in the source PDF file - see below
Here is the PDF Image after Import and Scaling
Here are the Vectors that were extracted
As you can see the Contour lines are longer and the Text Objects (in Yellow) at the end of the contours are in the Vectors but not in the PDF
While I would love to tell you that TBC is so smart that it can work this stuff out for itself, unfortunately it is much simpler than that - The PDF File must have data that is hidden in the PDF that is actually data that the TBC Vector Extractor can see and pull out of the file. I have seen this before with Inset Overlays - where they obscure part of the Plan below the inset - and when we pull out the vectors we get the Inset Vectors and the Plan Vectors that are hidden behind the Inset.
In this case the data that we are finding must have been on hidden layers in the source software or must have had a masking property applied to it in some way - but it is still being written to the PDF - So we see it and extract it.
No Smoke and Mirrors, No Magic, just TBC doing its thing