Adobe PDF 1.3 is not searchable for conventional book composition. Please, check for yourself. More then half the glyphs in an intelligent font file, beginning with Apple Hoefler Text introduced at the Apple World Wide Developer Conference in May 1992, has GID Glyph Identifiers and no CID Character Identifiers (UTF16, UTF8, long character identifiers). Only glyphs that have both GIDs and CIDs stay searchable (that is, they are drawn by the obligatory CMAP Character Map in the TrueType Specification).

Mac OS 7.5 in September 1994 introduced drawing of typographic ligatures, typographic small capitals, typographic superscripts, typographic subscripts and more without chaotifyng the source character string. Searching, spelling, and sorting have worked for a decade and a half no matter how complex the composition. In the Apple TrueType 2 model first demonstrated at the World Wide Developer Conference in May 1992, character codes are public and font-independent while glyph codes are private and font-dependent. This is also the model in Microsoft’s additions to TrueType, first named TrueType Open and then named OpenType.

Meanwhile,Apple is selling a million Macs a month, and it is easier to do so if as well the simple CMAP shaping as the supplementary Apple MORT/MORX and Microsoft GSUB shaping is supported in authoring applications that depend on system level services. The everyday enduser perceives Apple Mac OS X as a platform for advanced typography, but if the supplementary Apple MORT/MORX and Microsoft GSUB shaping is not searchable in PDF 1.3, and if the enduser is not told, then this is not moral marketing.

Microsoft Word for Macintosh 2008 only allows access to modern / common typographic ligatures in intelligent font files, only as a global on/off setting, and the setting is off by default. Apple iWork allows access to any supplementary shaping in the intelligent font file through the Apple Typography Palette, and modern / common typographic ligatures are on by default. There is therefore a proportionally higher loss of character information.

Unfortunately, if document descriptions do not perish in the memory of the printing system as the printed paper emerges, but persist on disk, then they must maintain the source character string as the style runs in the intelligent font file, and that is not happening for the supplementary shaping. The Type 42 Specification introduced in 1993 makes it legal to strip all tags except the font program tags, that is, the spline drawings. Thus the core of the intelligent font file format, the CMAP Character Map, may be stripped. The intact ICC tagged file format can be saved into PDF 1.3, but the intact SFNT Spline Font file format can first be saved in PDF 1.6, in Adobe PDFXML (Adobe Mars), and in Microsoft XPS.

Best wishes,
Henrik Holmegaard
would-be technical writer

Reference:
http://www.planetpdf.com/enterprise/article.asp?ContentID=6521

To see potential problems with products that support advanced typography features, such as ligatures, small caps and old-style numerals, see the Adobe OpenType User Guide, authored with Adobe InDesign and exported directly to PDF:

“2002″ is present in the first page below the title — but cannot be located as since old-style figures are used.
The SFNT acronym present in the first paragraph in page 2 cannot be located, as it uses small-caps.
“Microsoft” is present 5 times in this document — but none of the instances can be located due to the use of ligatures (ft in this case). Even the word “This” in the opening paragraph in page 2 (line before last) cannot be located due to the use of ligatures. The more common fi, fl, ffi ligatures are searchable in the case of this document, but this is not the case in other documents using these ligatures (this depends on the applications used to author/create the PDF).
While these OpenType features result in a superior typography, they should be avoided in online documents, until Acrobat Find and Search functions are enhanced to support the additional characters.

As an example for a PDF with text that is internally deformed, see the Adobe InDesign Programming Guide. It includes numerous code fragments (see pages 419 and onwards) set in a monospace font, and the same font is used in regular text to indicate function names or related items. All of these are not searchable. Copy and paste the text and you’ll see why: “matrix passed” is understood internally as “2#___A”.#%%_&”". With this type of document, users could have happily used the copy and paste function to reduce typing time/errors when studying or implementing the techniques discussed, but results in this case are of no value.