PdfHighlights - PdfHighlights extracts and exports all your PDF highlights and PDF annotations from all your PDF files into a single report.
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
PDFelement Pro - PDFelement Pro is a feature-rich and highly useful solution that enables you to modify, populate, convert, sign and annotate PDFs.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.
Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.