If you already use a CAD program

You already think in layers, snaps and scale. Most of it carries over; a few things are split differently. This is the translation.

A layer in CAD

In CAD one layer carries two ideas: how things on it LOOK (colour, line type, line weight) and whether they’re shown, locked or printed. Here the two are separate. A style is the look (a saved colour, weight and pattern, such as Length or Demolition). A layer is the set you show, hide and lock. A take-off group is a third thing again: a line of the bill.

Current layer

The layer you click in the Layers panel is where new markup goes, as the current layer does. With none picked, new markup goes under Not on a layer, which behaves like any other layer: it lists what’s on it and can be hidden and locked.

Lock a layer

The same idea: it stays visible and can’t be picked up or changed. Here a click on a locked item says so, and which padlock is on it. You can also lock a single item, wherever it is.

Properties

The Properties bar changes the colour, weight, pattern, fill and text size of what’s selected, or of what you are about to draw. Only the controls the thing really has are offered.

Object snap

Snap pulls a point to the drawing's own lines and corners, to marks you have made, and (hold Ctrl or Option) to the middle of nearby text. It reads the PDF's drawn lines; it isn’t a CAD model, so a scanned sheet has nothing to snap to.

Units and scale

A PDF has no drawing units. You calibrate each page by clicking both ends of a dimension you know and typing what it is. Every quantity then comes from the points you clicked and that scale, never from reading numbers off the sheet.

Areas and hatches

An area is the closed shape you trace, with cutouts for holes. A Fill an area click finds the enclosed region for you where the drawing has lines to find.

Counting blocks

Count places a marker each time you click. Count every one finds a symbol you have shown it across the whole set, and shows you every match before it counts.

Reference files

There are none. To see how one revision differs from another, use Compare: it lines the two sheets up by two points and shows what changed in colour.

Where it isn’t like CAD

• You’re marking up a picture of a drawing. Nothing you do changes the drawing's own lines; to correct the drawing, correct it where it was made.
• There’s no command line. Find (Ctrl+F) finds tools, commands and settings by name instead.
• Layers here aren’t part of the PDF's own structure unless you export them: they’re written out as layers of the exported PDF so another reader can show and hide them.

Layers, styles and locking, in detail ›