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PDF to DXF for Laser Cutting: Get a File That Cuts Right

Updated 30 October 2026

A clean PDF to DXF for laser cutting needs four things the PDF itself never promises: closed paths, no duplicate lines, the right units and text turned into outlines. Miss one and the laser cuts an edge twice, leaves a part hanging by a thread, or cuts a 100 mm sign at 3.9 mm.

Here is how to get each one right, from conversion to the first test cut.

What does a laser cutter need from a DXF?

Laser software treats every line in the file as an instruction. A CAD drawing can carry construction lines, dimensions and hatching; a cutting file can carry none of them.

Requirement Why it matters What goes wrong without it
Closed paths Kerf offset and inside/outside order work only on closed shapes Parts stay attached, kerf offset is ignored
No duplicates Every line is a pass of the beam Double burn, wider kerf, scorched edges
Correct units DXF stores no reliable unit Part 25.4 times too big or too small
Text as curves Fonts differ between computers Wrong font, missing letters
No fills or hatching Fills become engraving or extra outlines Unwanted engraving, extra cuts
Vector lines only Images can only be engraved Nothing to cut at all

Is your PDF a vector file or a scan?

Zoom in to 800% on a curve. Vector lines stay sharp at any zoom; a scan turns into blocky pixels. Logos from a designer, part drawings exported from SolidWorks or Fusion 360, and sign artwork from Illustrator are vector. A drawing someone photographed or scanned is a picture.

A scan imports into LightBurn as an image, which you can engrave but never cut. The guide on telling a vector PDF from a scanned one has more tests.

How do you convert the PDF to DXF at the right size?

  1. Drop the PDF into a free PDF to DXF converter that runs in your browser. The file stays on your computer, which matters for client artwork under NDA.
  2. Click Set scale and click both ends of something whose real size you know: the overall width of a sign, a hole spacing on a bracket, or a dimension line.
  3. Type the real length and pick the unit. A 600 mm sign gets 600 mm, whatever size it sits on the PDF page.
  4. Set the output units to mm, unless your laser software runs in inches.
  5. Press Convert to DXF and download.

The DXF comes out in the R12 format that every laser and CAM program opens, with one layer per line colour. When the designer marked cut lines red and engrave lines black, the layers PDF_FF0000 and PDF_000000 split cleanly into a cut layer and an engrave layer in LightBurn. Filled areas land on their own PDF_FILL layers, which you can delete in one go.

Without a scale, the drawing arrives at paper size. A logo that filled an A4 page (297 × 210 mm) arrives roughly 280 mm wide, whatever size the customer ordered.

Why do mm and inches cause trouble?

DXF files do not reliably record the unit they were drawn in. LightBurn’s own documentation warns that a 5 inch part can import as 5 mm. So:

  • In LightBurn’s Settings window, set the DXF unit to match the file before importing.
  • After import, measure one known dimension with the measure tool or the size boxes at the top of the screen.
  • If the part reads 25.4 times too big or too small, the unit is wrong. Fix the setting and re-import; scaling by hand leaves a rounding error on every hole.

How do you clean up the DXF in LightBurn?

LightBurn has four tools for this, all in the Edit menu:

  1. Delete Duplicates (Alt+D, Option+D on a Mac) removes objects identical in size, shape and position. Ungroup first, because grouped duplicates are left alone.
  2. Auto-Join Selected Shapes (Alt+J, Option+J on a Mac) joins segments whose end points sit within 0.05 mm of each other into one path.
  3. Select Open Shapes highlights everything still open, so you can find the gaps auto-join missed.
  4. Convert to Path (Ctrl+Shift+C, Cmd+Shift+C on a Mac) turns live text into curves, so the file cuts the same on any computer.

Run them in that order on every PDF-sourced file. A typical cleanup takes two minutes and saves a ruined sheet.

Why do PDFs produce so many duplicates?

Designers draw a shape as a fill plus an outline. The converter keeps both, so the shape edge appears twice: once as the outline, once as the boundary of the fill. Two parts drawn side by side in a nest also share an edge. Delete the fill layers first, then run Delete Duplicates on what is left.

How do you set kerf for a precise fit?

Kerf is the width of material the beam burns away. A CO2 laser in 3 mm plywood removes somewhere around 0.1 to 0.2 mm; your machine, lens, focus and material decide the exact figure. For tabs, slots and press-fit joints, that tenth of a millimetre decides whether parts slide together or fall apart.

Measure it instead of guessing:

  1. Cut a 20 mm square with Kerf Offset set to 0.
  2. Measure the square with calipers. If it reads 19.84 mm, the kerf is 0.16 mm.
  3. The offset applies to each side of the path, so enter half the kerf, 0.08 mm, as Kerf Offset in the Cut Settings Editor for that layer. LightBurn’s documentation also describes a kerf test pattern that reads the offset from a printed scale.

Positive values move the path outward on outer shapes and inward on holes, so both end up at drawing size. This works on closed shapes only, which is one more reason to run Auto-Join first.

Also measure the sheet thickness. Sheets sold as 3 mm plywood vary by a few tenths of a millimetre from batch to batch, and a slot drawn at 3.0 mm for a 3.2 mm sheet will not take the tab.

What about scanned drawings and traced outlines?

Tracing a scan turns the ink into closed outlines around both edges of every line. For a solid logo, that is exactly what you want: the outline of a filled shape cuts cleanly. For a line drawing, the laser cuts both edges of each ink line and leaves a hairline strip of material. Redraw those cut lines as single paths over the trace. The guide on converting a scanned drawing to CAD covers scan resolution and the redraw.

Laser or CNC?

The same rules about closed paths and duplicates apply to routers and plasma tables, with tool diameter taking the place of kerf. The guide on PDF to DXF for CNC covers CAM tolerances and joining polylines.

Pre-cut checklist

  • Units checked against one known dimension.
  • Fill layers deleted, duplicates removed, open shapes joined.
  • Text converted to curves.
  • Cut and engrave layers separated by colour.
  • Kerf offset set from a measured test cut.

Cut a test piece in cardboard first. It costs a few cents and catches every mistake on this list.

Questions people ask

Can LightBurn open a PDF directly?

Yes, LightBurn imports PDF as well as DXF, SVG and AI. A DXF still helps when the file goes to a laser cutting service, when you need it at a set size, or when other software in the shop has to read it.

Why does my laser cut some lines twice?

The PDF drew the same edge twice, once as a filled shape and once as an outline, or two shapes shared an edge. Run Delete Duplicates in LightBurn (Alt+D) before cutting.

Why is my DXF 25 times too big or too small?

DXF files carry no reliable unit, so a part drawn in inches can import as millimetres. Set the DXF unit in LightBurn's settings before importing and check one known dimension.

Can I laser cut a scanned PDF?

Not as it is. A scan imports as an image, which you can engrave but not cut. Tracing gives outlines around the ink, which cut as thin double lines, so redraw the cut lines first.

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