Wrap text should work fine when exporting to pdf, but what FlexCel doesn't do by default is to autofit rows. To fix it:
If you are using XlsFile, call:
xls.AutofitRowsOnWorkbook(...)
before exporting to pdf.
If you are using reports, write this tag:
<#Autofit Settings(All, keep, 100)>
Somewhere in the template sheet you want to export.
Autofitting is a complex theme, if you want more information, please read "Autofitting Rows and Columns" in UsingFlexCelApi.pdf, and take a look at Demo\CSharp\Modules\20.Reports\85.Autofit