Convert a PDF drawing to CAD lines (DXF) for free, at the right scale

When a drawing arrives as a PDF but you need a DXF for laser cutting or further editing, the lines can be recovered completely — as long as the PDF was exported from a CAD program rather than scanned. In DXCAD2D Online you open the PDF with File → Open file…; lines, text, table rules and arrowheads come in on a layer called PDF. Scale once to true size and export a DXF.

Two kinds of PDF — know which you have

Many files are mixed — a CAD drawing with the company logo as a picture, for instance. The vector parts become lines and the pictures stay pictures.

Converting a vector PDF to CAD lines

1. Open DXCAD2D Online, choose File → Open file… and pick the .pdf (or drag it onto the page).
2. If it has several pages you are asked which: type 1, 1-3 or 1,3,5. Multiple pages are laid side by side to the right.
3. Everything lands on the PDF layer. Text stays editable text, table rules and arrowheads come in, and line colours follow the original.
4. Scale to true size (next section) — the most important step.
5. Delete what you do not need. For a cutting file that means the frame, title block and dimensions, leaving only the part outline.
6. Export as DXF (R12, mm).

Scaling to true size

A PDF stores sizes on the paper, not sizes of the part. The import uses millimetres on the paper, so a drawing printed at 1:1 is already true size, but one at 1:2, 1:5 or "fit to page" must be scaled back up. The most reliable way is to use a known dimension:

1. Find a line with a dimension written on the drawing — the longer the better, such as an overall length of 450.
2. Measure that line with a Dimension (D) with object snap on (F3) — say it reads 90.00.
3. Work out the factor = true size ÷ measured size = 450 ÷ 90 = 5.
4. Select everything (Ctrl+A), type SC (Scale), click a base point, type 5 and press Enter.
5. Measure the same line again plus one dimension at right angles to it; both must match the numbers on the drawing.

Scanned PDFs: tracing the picture

If the PDF is a scan, the picture is placed where it was on the page. Then:

1. Scale the picture to true size first, the same way as above.
2. Select it and type TC (Image → CAD). Choose the line drawing (plans/sketches) mode and adjust the black/white threshold and resolution as needed.
3. The result is polylines that follow the picture. They are good as a reference to redraw over, not for cutting directly: straight lines will not be perfectly straight and circles will be faceted.

For scanned drawings, the most dependable result comes from redrawing with real lines, circles and the sizes written on the drawing, using the picture as a background.

Common problems

• Circles turn into several curve pieces. PDFs have no true circles, only Bézier curves. Most are turned back into circles or arcs, but some files leave several segments. For accurate holes, draw a new circle on the same centre.
• Lettering looks different. The PDF's font may not be available, so a font with similar widths is used. Text positions are right, but letter shapes may differ slightly.
• Text arrives as solid shapes. Some PDFs already turned text into outlines; those come in as fills and cannot be edited as text.
• Doubled lines. Some programs draw the same line twice. Before laser cutting, check and remove duplicates — see preparing drawings for laser cutting.

In short: PDFs from CAD convert to lines very well — just check the scale against a known dimension every time. For scanned PDFs, use the picture as a reference and redraw. And if you can, ask the sender for the original DXF.