How accurate is the PDF to CAD converter?

The short answer: a vector PDF converts with no measurable error, the scale tool adds a few hundredths of a percent, and a traced scan is good to about half a percent. Those numbers come from five test drawings we drew with exact sizes, ran through the same converter you use on the home page and measured in the DXF with ezdxf, the open-source Python library for DXF files.

0.001 mmlargest outline error on the vector test files

0.036 mmlargest circle deviation (30 mm bore)

0.036%scale tool error, two clicks on a 10 m wall

0.4%traced scan, 200 dpi, skewed 0.4 degrees

Which drawings did we test?

Test file	Sheet and scale	What it checks
Machined plate	A4, 1:1	120 x 80 mm outline, four 6.5 mm holes, a 30 mm bore
Laser-cut sign	A4, 1:1	200 x 100 mm rounded outline, 5 mm holes, curves
Floor plan	A3, 1:50	10 000 x 7 200 mm apartment, doors, text, dimensions
Floor plan, scale tool	A3, 1:50	the same plan scaled with two clicks in the browser
Scanned floor plan	A3, 200 dpi	the plan printed to an image, skewed 0.4 degrees, traced

Each file was made with reportlab, a Python PDF library, so the true size of every line is known. The three vector files were converted with the converter code itself; the scale tool and the scan went through the live converter in Chrome, the same way you would use it.

How far off is each test?

Error on the longest outer edge, in millimetres

Error on the longest outer edge, in millimetres

Machined plate	0.0 mm
Laser-cut sign	0.0 mm
Floor plan	0.0 mm
Floor plan, scale tool	3.6 mm
Scanned floor plan	38.0 mm

The vector results are exact because the converter copies the coordinates the PDF stores and multiplies them by one factor. The only rounding is the DXF’s six decimals.

How round are the circles?

A PDF stores a circle as four Bezier curves, and the DXF R12 format has no Bezier, so each curve becomes 12 straight segments. The question is how far those segments stray from the true circle.

Largest deviation from a true circle, in millimetres

Largest deviation from a true circle, in millimetres

5 mm hole	0.006 mm
6.5 mm hole	0.008 mm
30 mm bore	0.036 mm

For CNC milling of large arcs, a curve-fitting step in your CAM program (or the CAD command that converts polylines to arcs) gives true arcs again.

What do the files look like?

Can I check the results myself?

Yes. Download the test files, convert them here and measure the DXF in your own CAD program.

The handbook explains the full test method, including the scoring we use when we compare converters: how we test PDF to CAD converters. For what happens to a PDF inside the converter, read how the converter works.

What can still go wrong with your own PDF?

• Printed with “fit to page”. The PDF is then a few percent smaller than the scale printed on it. Set the scale from a long known dimension and the error disappears.
• Text turned into outlines. Letters arrive as shapes. Their size is right; you just can’t edit them as text.
• Several scales on one sheet. A detail at 1:5 next to a plan at 1:100 needs two conversions, each with its own scale.

Convert a PDF to DXF now

Questions about pdf to cad converter accuracy

Can I trust the measurements in a converted DXF?

For a vector PDF, yes: our test outlines came back exact to 0.001 mm at paper size and at 1:50. Check one known dimension after conversion anyway, because the PDF itself may have been printed with fit to page.

Why is the scale tool slightly off?

You pick the two points by clicking, and a click lands within a pixel or two of the line end. On a 10 m wall that cost 3.6 mm (0.036%). Zoom the browser in and click on long lines for the best result.

How accurate is a traced scan?

Our scanned floor plan came out 0.4% too large (38 mm on 10 m), because tracing follows the outside of each ink line and the scan was skewed by 0.4 degrees. Redraw over the outlines for anything you build from.