After Imposition Type (discussed in Section 01) come the fields that define the layout geometry of each side of the output sheet.
Layout Units can be specified to be cm, mm, points, or inches.
The Marks On checkbox tells whether printer marks are on or off. See the Marks panel, discussed later.
Page Trim Width and Height are the width and height of the pages of the InDesign Source document.
Number of Pages Across and Down (Layout Columns and Rows) define the page grid on the sheet. For example, for a Saddle Stitch booklet, there are 2 columns and 1 row on each side of a sheet. Or you’re using Step and Repeat to do sheets of business cards, a sheet might have 2 columns and 4 or 5 rows. (The PageSequence files each define a set number of columns and rows.)
Horizontal and Vertical Spacing
Horizontal Spacing is the desired distance between the columns of source pages (or cards or labels or whatever). Ignored if there is only 1 column of pages.
Similarly, Vertical Spacing is the distance between the rows of source pages. Ignored if there is only 1 row of pages.
If the desired spacing is not uniform, the horizontal spacing can be a list of values, like this 4×2 example. Here, the horizontal spacing is set to be “0, 0.5”. This will give zero space between the pages of the first spread, then a 0.5″ horizontal space between spreads, then zero space again between the pages of the second spread. (I know that it looks like I forgot to include the final zero, but any ‘partial patterns’ are automatically repeated as necessary, so the (0, 0.5) pattern is repeated with another zero.)
There are only 2 output rows, so we’ll put 0.5″ of vertical space between the rows, which we might do if bleed was specified in the InDesign Document Setup.
And here is the first sheet of the resulting output from a test document:
Total Trim Size
The Total Trim Size and Total Trim Plus Marks tell you how much space is taken up on the sheet with the individual Page Trim dimensions plus the Spacing.
Paper / Sheet Dimensions
Suggested N.Am / Metric paper size finds a standard sheet size that is large enough to accommodate the TotalTrimPlusMarks size. But you can override the suggested paper size dimensions by typing directly into the Sheet Width / Height boxes.
Sheet Margin Left is automatically calculated to be the space between the left edge of the output sheet and the left edge of the TotalTrimSize. Similarly for Sheet Margin Right, Sheet Margin Top, and Sheet Margin Bottom.
If you need unequal horizontal or unequal vertical sheet margins, you can type directly into the edit boxes. And don’t forget that the actual output Sheet Dimensions will be whatever is in the Sheet Width, Height boxes.
Miscellaneous Commands dropdown
Under these sheet geometry layout controls we have the Miscellaneous Commands dropdown:
“Save layout as .geo” and “Apply .geo layout file” are experimental.
“Save all settings as .json” and “Apply .json settings file” save and apply most of the settings of the Layout, Options, Marks, and Freezing panels.
The ‘sidecar’ .sc folder
By the way, these same settings are automatically saved in a ‘sidecar’ folder, named <docName>.sc, every time you click the “Impose” button or the Cancel button. That last bit of behavior probably violates general UI guidelines; but it is extremely annoying to type a bunch of layout settings, Cancel, and then have to type everything in again.