π Quick PDF to DXF conversion
The most common format for sharing drawings is PDF, but it does not allow further editing. However, it is possible to convert a PDF drawing to DXF. Such a format can already be edited, but more importantly used as a basis for HiStruct. Here is a list of online tools for this conversion that are free:
Or even desktop applications:
You can then use the generated DXF files for import into HiStruct.