Bookmark PDFs

I have Adobe Standard DC and I can't bookmark my pdfs. There is no bookmark+ icon in the bookmark section. I had Standard, a DC trial was pushed to my computer, when it expired, my version no longer worked, I bought and installed a new version (Standard DC) and I still can't bookmark. I don't need pro, all I use are bookmarks and comment tools. I've tried to repair installation, uninstalling all Adobe software, reinstalling. I've even tried to repurchase and it won't let me because I have the right version but it's acting like reader. What do I do??!! I have work due this week and I can't do it!