Notes and annotations are meant to be used. Set your intention - whether it is comprehension, exam preparation, brainstorming, or something else - and use your notes to work toward it. See The BEAM method for an example of it in practice.
The practice of (physical) note taking promotes metacognition. Your learning will be enhanced by spending 5 minutes reviewing your own notes on the same day you create them. See Cornell Notes for an example of it in practice.
Reading strategy: Don't read every word. Instead, make informed decisions about what to read based on your goals.
1) skim the abstract, and if it still looks good...
2) skim the introduction and conclusion ONLY, and if it still looks good...
3) take a high level view of the article - use your goals to identify relevant sections (method, analysis, etc.) and skim those, and if it still looks good...
4) THEN consider reading the whole article.
Zotero is one tool to help facilitate reading and note taking. With the latest version, Zotero 6, you can attach and read PDFs in Zotero, with the options to:
Additional Zotero features include cloud storage, group libraries for research collaboration, filtering by tags, and integration with Microsoft Word and Google Docs.
Mendeley provides similar functionality to Zotero. In Mendeley, when you have a reference with an attached PDF, double click on the PDF icon or citation to open Mendeley's PDF Reader where you can: