Wrong lineweights in the PDF: pen settings and CTB

The drawing looks right on screen and the print comes out flat: every line the same weight, a wall no heavier than a service run, the title block gone. After hatching, this is the second most asked print problem, and the cause is nearly always where the pen settings are read from.

Thickness is defined in three separate places

1. The layer's lineweight

Every layer carries a thickness — 0.13, 0.25, 0.50 mm and so on. An object set to "ByLayer" takes its weight from there. This is the only value stored inside the file and read the same way everywhere.

2. The object's own lineweight

A weight assigned directly to an object overrides its layer. Half the confusion in a drawing you received starts here: the layer says 0.25 and the line prints at 0.50.

3. The pen table (CTB / STB)

This is what actually decides, and it is not inside the file. A CTB works by colour: "whatever is red, print at 0.35 mm". An STB works by named style. The long-standing habit in AutoCAD is CTB — which means an office's print standard lives in a .ctb file on that office's machine, not in the drawing. Send the drawing elsewhere and the table stays behind.

Why everything comes out at one weight

• Lineweight display is off. The screen shows no thickness while the print has it — and the reverse happens too.
• The pen table is set to none. With no table selected in the plot dialog, everything prints at the default weight.
• Scale. On a sheet printed at 1:100, 0.13 mm is already below what the eye resolves; the thinner the scale, the higher the floor has to be.
• The converter never reads weights at all. Many online tools draw all geometry with one default pen. The tell: if a wall and a grid line are indistinguishable in the output, no weight was applied.

Practical values by scale

A common architectural convention: walls cut in section 0.50–0.70 mm, visible edges 0.25–0.35 mm, grids and dimensions 0.13–0.18 mm, hatching on the thinnest pen. Below 1:200, merging the two thinnest pens keeps the sheet readable.

When you send the file

If the drawing is going out to be printed, send a scaled PDF with it. The recipient does not have your pen table and will never see the sheet you see; the PDF is the only page both sides agree on. You can attach your CTB too, but the other side has to drop it in the right folder — and in practice most people do not.