Formatting Your E-Book with Adobe Acrobat

by Geoff Hart

Adobe Acrobat produces PDF files that readers can use on any computer with the free Acrobat Reader software, and these files offer all the advantages of printed books: with Acrobat, we can now produce online documents whose visual design benefits from centuries of research and experimentation in book design.

For the first time, we can choose typefaces for online information that convey a specific "look and feel" and meet our legibility goals without worrying about whether our audience installed those typefaces on their computer. For the first time, we can combine white space, text, and illustrations to produce an attractive, readable document-- readable by people who don't own the software we used to create the file-- and without worrying that they'll resize the window and destroy the whole design. For the first time, we can produce documents that display on printers or computer monitors at the device's best resolution.

So if Acrobat's this great, where's the trouble? It lies in misunderstanding the software's purpose and inherent limitations.

There are two main reasons to use Acrobat:

• to distribute documents for printing,
• to control an online document's layout and typography so that it communicates as effectively as its printed equivalent.

Mismatched media

The second reason is what makes Acrobat most interesting, and what causes readers the most grief. Why? Because designers forget that a single document designed for print only rarely serves as an acceptable source for an online document. This "single sourcing" is one of the holy grails of technical communication, since it would provide twice as many products for a single product's investment in labor. Unfortunately, single-source documents are only possible using technologies such as SGML; Acrobat can't fill this need because once you've chosen the document dimensions for a PDF file, readers can no longer alter this size. That limitation, unfortunately, greatly reduces the possibility of single-sourcing with Acrobat.

Consider, for example, documents designed to print on North American letter-sized paper (8.5x11 inches) without wasting enormous amounts of paper. Such documents won't fit comfortably on a standard 14-inch monitor (around 10x7 inches); 3.5 inches of the text remain unreadable below the bottom of the screen until readers scroll downwards to see the hidden text, or resize the document to fit on the screen, thereby reducing the type to illegibility. You could instead design the document in "landscape" format, with the longest dimension running horizontally, but that still sacrifices 1 inch of width and 1.5 inches of height on the page if you also intend for readers to print the document. Moreover, that design doesn't match the dimensions of European A4 paper, which is widely used outside North America. Even if you do produce a landscape-orientation design that works equally well on both paper sizes, the format is unfamiliar to most readers; it thus makes for an uncomfortable choice, particularly when placed in standard binders.

This problem arises from a mismatch between paper and the online medium, not from any inherent limitations of Acrobat. You can certainly optimize PDF files for on-screen reading--provided that you take the same care you'd take in designing any other page layout. Fortunately, that's not a difficult task. Taking full advantage of Acrobat to produce successful online documents involves four steps:

1. Pick an appropriate "page" size

The appropriate "page" size for any online document is one that fits comfortably on a standard monitor. Many designers use 19- and 21-inch screens, and forget that most computer users only have 14-inch monitors. To fit comfortably on the smaller monitors, the ideal page size must be less than 10 inches wide by 7 inches tall. If you anticipate that many readers will use the document on laptop computers, pick a slightly smaller size.

How can you tell what screen size to design for? Check the ads for computers sold locally and by major international vendors such as Dell. So long as 17-inch or larger monitors are extra-cost options for desktop computers, and 14 inches remain the maximum screen size for laptops, you must design for the smaller screens. Even once larger screens become the standard, expect to wait at least 3 years before most computer users have replaced their old screens with larger ones.

2. Choose appropriate fonts

There's a myth that sans serif fonts such as Arial or Helvetica are inevitably easier to read online than serif fonts such as Times and Garamond, and this myth leads many designers to use sans serif fonts blindly in all their online information.

In point of fact, sans serif fonts represent an unfamiliar choice for large expanses of body text for most North American readers, and can thus be both uncomfortable and more difficult to read. (On the other hand, French and Nordic readers are quite comfortable with sans serif fonts in body text, but also have considerable experience with serif fonts from reading English publications.) This being the case, serif fonts may be a better choice, particularly if you anticipate a primarily North American audience.

Well-designed serif typefaces are generally more legible than sans serif fonts, even on screen, because of the greater visual differentiation among the letters. With older monitors, the comparatively low resolution often blurred or eliminated the serifs of serif fonts that had been designed for print. But newer monitors and serif fonts designed specifically for on-screen viewing (most TrueType fonts, for example) minimize or eliminate this problem.

Selecting a slightly larger type size for online viewing than you would use in print eliminates any traces of this problem that might remain, and makes serif fonts a perfectly acceptable design choice. Using slightly larger type makes good sense no matter what typeface you choose, since even the sharpest screens have lower resolution and contrast than printed materials, thereby making on-screen reading more fatiguing than reading on paper.

3. Use white space appropriately

Choosing an appropriate line spacing (leading) lets readers easily scan from the end of one line to the beginning of the next without skipping lines. To avoid the problem of skipped lines, choose a slightly greater leading than the default values in the software you're using to produce the Acrobat file. ("Space and a half" or double-spaced text is too open, and wastes space.) To pick a suitable leading, try reading your text quickly, and if you find yourself occasionally skipping lines, increase the leading and try again until you stop skipping lines.

Line length is closely related to line spacing, since wider lines require more line spacing to prevent the problem of skipped lines. Designers have found that the optimal line length averages about 65 characters; you may have heard this described as the "two and a half alphabets" rule, because 2.5x26 characters =65 characters.

At a typical viewing distance and with typical type sizes for body text, this rule describes the maximum number of letters that fit within a single visual field. This choice of line length facilitates reading by minimizing eye motion during reading; it also ensures that the beginning of the next line remains within your field of vision, thereby reducing the risk of skipping it when you finish the current line. Overly narrow columns have a different effect, since they require more back and forth eye movement; readers reach the ends of short lines more frequently and have to swing their eyes back to the beginning of the next line.

If you use a multi-column layout, separate the columns a bit more widely than is necessary in print so that readers in a hurry don't inadvertently scan across into the second column. (Don't worry about wasting space; unlike paper, electrons are cheap.) The constraints of larger type size and a relatively narrow screen display can make it difficult to fit two acceptably wide columns side by side on a typical screen. If so, consider choosing a single-column design and using any left-over space to improve the esthetics of the screen by including appropriate graphics or pull quotes in the space not filled by text. A single-column design also lets you use larger type than would otherwise be possible, producing an even more legible design.

4. Take full advantage of the online medium

Following the first three steps produces a document that's well formatted and easy to read, but stopping there fails to take full advantage of the strengths of the online medium and doesn't compensate for its weaknesses. For example:

• Unlike Web browsers, Acrobat doesn't let readers redefine the typeface, type size, and other typographic specifications, nor does it let them resize windows without pushing some of the page outside the window. Readers can improve the view of a Web page designed in 7-point magenta type on a chartreuse background by changing their browser settings, but if you're unfortunate enough to receive a PDF file in that format, you're stuck with it. You can zoom in to make the text more legible, but you can't change the typeface or the colors. That being the case, restrain your artistic urges and choose a design that emphasizes readability over stylistic excess.
  
  
• A design that relies on a fixed "page" (window) size works poorly on monitors that can't display the full page without endlessly scrolling or shrinking the page to the point of illegibility. Moreover, documents that must remain visible on-screen at the same time as another program, as in the case of a PDF file that displays explanations of the controls for an online instrument panel, must fit on-screen beside the other program without either concealing the controls or becoming unreadable.
  
  
• Acrobat lets readers search the text and follow links to related topics, but full-text searching is an extremely poor substitute for a professional index. Moreover, Acrobat only automatically generates links to chapters and main headings; don't forget to create links such as "see page 9", "as discussed in Chapter 10", and "as shown in figure 11" manually.

What's the bottom line? When you choose Acrobat to distribute documents, carefully consider both your goals and the reader's needs. You can produce something that prints well or something designed for onscreen use, but a single document can only rarely fulfill both goals. "One size fits all" works for stockings, but produces suboptimal documents that never work as well as documents designed specifically for online or in-print use.

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