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Kindle look-up dictionaries should work with all pdf books regardless of how they have been acquired or delivered to Kindle.
However, user may come across three pdf varieties:
1. Scanned, that is, purely graphic, no text layer
2. Text layer is present but explicit delimiters (spaces) between words are missing.
These pdfs have words just drawn at predefined positions inside the text line.
3. Text layer is present and words are delimited by space characters.
Apparently, highlights and look-up dictionaries are disabled in
first type pdf.
Situation becomes ambiguous with
pdfs of second type.
Second type pdf is created, for example, by Prince XML software (
www.princexml.com)
when full justification is applied during pdf generation.
E-readers that use Adobe Mobile Reader to display pdf cannot use look-up dictionaries with pdf of second variety due to error in Adobe Mobile Reader (desktop Acrobat reader doesn't have this error).
For example, all Sony readers, Pocketbook, and Kindle Keyboard (not sure about Kindle NT) use Adobe Mobile Reader.
Interesting that Kindle Paperwhite (evidently) doesn't use Adobe Mobile because look-up/highlight is working on Paperwhite with second type pdfs.
In conclusion, look-up dictionary works on all readers with
pdf of third type. By the way, MS Word 2007 and later always generates third type pdf.