The Sorl search platform has a configuration field that prevents some words from beeing indexed. Words like an, and, are, as, at, be, but, by, if, in, their, etc are not indexed. This also affects the result highlighting in the DocuWare web viewer.
The default path of the file is following (32/64bit fulltext server):
C:\Program Files\DocuWare\Full-Text Server ((x64))\webapps\solrt\solr\conf\stopwords.txt
Please be aware of that the changes will only affect new stored documents. Also the fulltext server has to be restarted after the changes.