Welcome to the forum!
Not necessarily easy for anyone! There are a lot of different considerations in converting any raster image to vector. Your ultimate goal for the result is probably the most important factor in deciding how to proceed.
I guess you must have used Trace Bitmap to get the proper paths that you need? Depending which options you used in that dialog, you can probably change some of them, and get a better result. Like for example, if you used Brightness Cutoff, notice the Threshold value. You can raise or lower that number. While it can make the lines thicker or thinner, it might not necessarily make them any smoother. But it's certainly worth a try.
Also, check out what's available on the Options tab. I think Optimize Paths might help. Also, the larger and higher resolution of the original, the better result you will get. Because once you have the vector paths, of course they can be scaled without losing any quality or distortion.
There are several reasons why Trace Bitmap might not be the best way to convert the blueprints. For example, if you need precision, in addition to clarity, I would suggest Not using Trace Bitmap. Another reason is that the lines might always end up jagged, even in the best possible results. But the biggest reason is that Trace Bitmap won't give you a single path for a single line on the blueprint, as you might expect. It gives you 'double lines' (so to speak), which are a path on the outside of the line and a path on the inside of the line. It's much easier to understand by looking at the results with the Node tool, than it is to explain it.
You can still use an auto-trace, and get the single path, by using a centerline trace option. Trace Bitmap does not have a centerline trace, but there are other trace engines which do. (One is a web-based tracer:
http://www.roitsystems.com/cgi-bin/autotrace/tracer.pl and there are others which I think you can install locally.) However, even centerline trace has it's own problems. It doesn't handle line intersections very well.
So if you need precision and clarity both, the best option would be to 'manually' trace the lines, using Inkscape's Pen/Bezier tool. Especially if the blueprints are primarily horizontal and vertical lines, it can go very fast.
Of course I realize you didn't mention what your ultimate goal for the image will be. But I thought these things are worth mentioning, before you spend a lot of time, only to find in the end, that you just can't get an acceptable result.
Let us know if you have more questions :-)
Jingle bells!!
