First, please note that drawings are almost always drawn in real size (1:1) with a CAD system. If this is not the case, please correct your drawing first.
1. Open the DXF/DWG file with QCAD.
2. Edit > Drawing Preferences
3. Check and adjust 'Printing > Page > Paper Size' and 'Scale' (if known):
3. File > Print Preview
4. If the desired scale of the drawing is NOT known, click the button to adjust the drawing scale to the chosen paper:
5. Optionally, adjust the scale to the accurate, desired scale (10:1 in this example):
6. Optionally, adjust the paper position using the tool 'Move Paper Position':
7. To print the drawing, choose 'File > Print'.
8. To export the drawing to PDF, choose 'File > PDF Export'.