Good results from a phone photo of a printed plan:
- Photograph it flat, from straight above, in daylight. Avoid shadows across the paper.
- Trace → add the photo. Then click both ends of the longest dimension you can read and type its length. The longer the dimension, the more accurate the scale.
- Straighten it against a long outer wall.
- Fade it so your walls stand out, then draw the outer walls first and the rooms after.
For a PDF, pick the page; it comes in at 1:100 until you set the scale yourself.