Search pdf for 'eight' but not 'weight'

Select Edit > Advanced Search

Select "Match Exact word or phrase", then tick the "Whole words only" option.

Apparently this is only in Adobe Reader X (sorry).

In Adobe Reader 9 it's Edit > Search (Shift+Ctrl+F)

Adobe Search menu

There's no drop down but there is the "Whole words only" option:

Adobe Search options


Most search engines will consider exact match if you surround the text with " like " eight "


Keep your software up-to-date, Adobe Reader 9 has bugs and security leaks.

Here is a screenshot of Adobe Reader X:

enter image description here

As it looks like they slightly revamped the search engine it might support the " " syntax as well...