If your browser search and homepage gets redirected to search.doc2pdfsearch.com, be wary because this is a fake search engine. It is caused by the Doc2PDFSearch browser hijacker. Search results will send you to malicious websites to get money from you or infect your computer further. It may also modify and prevent you from changing your settings back.
Search.doc2pdfsearch.com is usually installed through bundled software without you knowing. Remove it immediately.