Newer ADE versions, like the 1.8 preview (is it still a preview? is it still available?) or the embedded versions in newer readers can hyphenate. It's not a perfect feature (my reader will sometimes leave a single letter in a line, or insert a hyphen between a letter and a punctuation character), but it won't allow words to overflow a line.
Or you could use a
zero-width space (& #8203;), but that's inserting special characters.