Hack 59 Crop Pages for Clarity

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Aggressive page cropping ensures maximum on-screen clarity.

When viewing a PDF in Reader or Acrobat, the page is often scaled to fit its width or its height into the viewer window. This means you can make page content appear larger on-screen by cropping away excess page margins, as shown in Figure 5-6. Cropping has no effect on the printed page's scale, but it might alter the content's position on the printed page.

Figure 5-6. Cropping pages to improve on-screen clarity

Acrobat's cropping tool can remove excess page margins. Use it in combination with our freely available BBOX Acrobat plug-in. These two tools make it easy to find the best cropping for a page and then apply this cropping to the entire document.

5.10.1 Acrobat's Crop Tool

With Acrobat's Crop tool, shown in Figure 5-7, you can draw a free-form crop region by clicking the page and dragging out a rectangle. Double-click this new region or simply double-click the page and the Crop Pages dialog opens. The Crop Pages dialog enables you to directly enter the widths you want to trim from each margin. You can also specify a range of document pages to crop according to these settings. The Remove White Margins setting sounds like just what we need, but it is inconsistent and it yields pages with irregular dimensions.

Figure 5-7. The Crop tool on the Advanced Editing toolbar in Acrobat 6 (left) and on the Editing toolbar in Acrobat 5 (right)

Using the Crop tool to draw a free-form region gives you an irregular page size that probably doesn't precisely center your content. The solution is to activate the Snap to Grid feature (View Snap to Grid). By default, this grid is set to three subdivisions per inch. A more useful setting might be four or eight subdivisions per inch.

In Acrobat 5, high-precision cropping requires using points instead of inches, because 1/8-inch increments get rounded to two decimals. In the File Preferences . . . Display dialog, change Page Units to Points. There are 72 points to an inch, or 9 points to 1/8 of an inch.

5.10.2 BBOX Acrobat Cropping Plug-In for Windows

BBOX is a simple tool I use in my PDF production. Download it from http://www.pdfhacks.com/bbox/, unzip, and copy pdfhacks_bbox.api into your Acrobat plug_ins folder [Hack #4]. When you restart Acrobat, it will add a menu named Plug-Ins PDF Hacks BBOX (the contents of which are shown in Figure 5-8).

Figure 5-8. Using BBOX to quickly eliminate excess page margins and gutters

The BBOX Auto-Crop feature crops as much as it can from the currently visible page. It trims away multiples of 1/8 inch (9 points), so the resulting page size isn't irregular. It tries to be smart, but it sometimes leaves margins that need additional cropping.

The Trim Page features enable you to trim 1/8 inch from the left or right page edges. If you go too far, use the Extend Page features to add 1/8 inch instead.

Sometimes 1/8-inch units are not fine enough to center a page. For these cases, we have the Bump Page features. These do not alter the page width, but appear to move the page one point at a time. They simply reduce the crop on one side and increase the crop on the other, giving you fine control over page centering.

5.10.3 Document Cropping Procedure

Does your document jog back and forth from one page to the next? Then you have page gutters. You will need to crop your even pages separately from your odd pages.

Find a representative page and crop it to your satisfaction using any combination of the Crop and BBOX tools. If your document has gutters, turn to the next page and give it the same treatment. Flip back and forth between these two pages as you work to remove the gutter, trying to get the pages to stop jogging back and forth.

When your representative page is cropped to your satisfaction, open the Crop Pages dialog by selecting the Crop tool and double-clicking the page. Set the page range to All Pages. If you are cropping even and odd pages separately, set the nearby drop-down box to Even Pages Only or Odd Pages Only depending on which page you currently have displayed. Click OK. Even and odd in this context refer to the physical page numbers (or page indexes) in your document, shown in Figure 5-9, not the logical page numbers (or page labels).

Figure 5-9. Using the physical page number, shown in parentheses, when cropping pages (this one is even)