This is a “common” issue with “existing” 3D PDF, that generally contains only Graphical information. So when you try to convert it to a “Geometrical format”, like STEP, it converts all the triangles to surfaces and the file size is huge at the end…
I faced to this issue this mistake when I started with Converter…You can “check this” following this process:
- Open the Model Tree
- Click on the Options icon
- Set Show Physical Properties
Then click your part in the 3d Annotation --> In the Model Tree, last section, you will have now more info about the part…If the Property Node info is Geometry, you would be able to “export” your model to CAD format…IF there is nay other result (Faceted solid, Tessellation, or no info!!), it means that the Geometrical export will be not possible.
To “work” on original file and split it (but it will have no impact if your initial data are Geometrical), I am using Tetra4D Reviewer, the companion tool of Converter, that allows me to open the original file, clean it and export only some parts in STEP file…once again, of course if this is possible to do, that means get Geometrical info to export
Hope this will help you,