Let me try to sum this all up. Some of this is from memory so don’t throw anything if I make a mistake.
First, let’s talk about how PDFs are used in printing. E10 asks SSRS to render a PDF. That is 100% handled by SSRS. That seems to have stayed very stable across the versions of SSRS. Somewhere above in the thread it was asked to email the report so you could get the actual PDF. You could also save from System Monitor even after it is printed. These, as far as I know, would stay identical across the different versions of SQL Server and not be affected by the version of E10.
The next part is where all the trouble comes in. As @hkeric.wci just stole my thunder, we use PdfPrintingNet.dll from https://www.pdfprinting.net/. Here’s the versions I checked:
2.0.0.0 = 10.1.500 and before
3.0.6.3 = 10.1.600 - 10.2.200
4.7.3.0 = 10.2.300 - future!
In the version switch from 2.0.0.0 to 3.0.6.3, they changed how they were scaling by default. We did our best to get it to match what the previous version did. I didn’t directly deal with this issue, and don’t clearly remember all the conversations. It was decided that we would keep the newer version for a number of bugs it fixed.
As I mentioned, I didn’t directly deal with customers to solve the scaling issues. Most reports don’t matter since the difference is small. Preprinted forms are where the problem is. If anything moves or changes size, it won’t match the preprinted form. I think the solution was to modify the SSRS RDL so that it fits with the new scaling.
I think the size difference (7mb to 28mb) comes from them adding a PDF viewer. I wish that would have been in a separate DLL since we don’t use that functionality at all.
EMF vs PDF was brought up because E10 “owns” the previewing and printing parts. This is analogous to PdfPrintingNet.dll and whatever PDF viewer you use. The scaling, etc. should be the same for EMF through the different versions of E10. I haven’t heard any issues with it, but then the default is PDF so I don’t know how much it is being used.
I think that may cover most of the points in the thread. Let me know if I missed something and I might be able to fill in more information.