There are quite a few good online PDF editors that are free. A few I can recommend are. What I’ve realized, though, is that some apps will be really good in one area but lacking in another. Some apps might be great for collaboration but not so good for editing. Some only work on Windows while some are designed exclusively for Mac and iOS. Some are just limited in their features. I have honestly found the best free online PDF editor to be Kdan PDF Reader. I really like its functionality and simplicity. It makes editing, converting, and creating PDFs really efficient. PDF Reader is free and works on Android, iOS, MAC, and Windows which makes switching between mobile, PC, and MAC easy. It really has the most editing features I’ve seen in a PDF editor. There are also other great features that make it an enjoyable experience for me like working with audio and video files. It automatically syncs with your Kdan Cloud which helps with organization and accessibility. Check out those editors I mentioned in the list above and see what works best for you. I hope you find one you like! Disclaimer. I am part of Kdan’s team and my answers might be a bit biased.
My favorite is not free but a paid one. It is a personal preference and one you will have to decide on your own. One other note. There is still a lot of learning that goes into this process, just like with any other skill. That is why I highly recommend you take a full-scale mock analysis from a professional. When I started out, I found that my experience was way too dependent upon one individual who told me what I needed to do. That person is only as good as you are. So get some feedback from people who know what they are doing.