I would really like an application for Windows and/or Linux that can view and do simple annotations on PDFs, JPGs, PNGs, and other file types quickly.
For example, in Mac Preview, if I open a PDF of some ebook, I can simply left click and drag over the section of text that I want to annotate, then right click the selected section to get an small options window of what kind of highlight color I would like to apply or if I want to apply an underline to the text, I select from the fixed selection on annotation options, and the menu closes on its own. Mac Preview also has the option to add text annotations onto/on top of the PDF or basic drawing or shape on the PDF.
All of this is done to the same PDF file, rather than having the annotations stored on some separate file that stores the annotations to be applied when a specific application opens that associated PDF (which is what the Okular viewer does in Linux). I know that Okular has the ability to save annotation onto the PDF itself (by exporting the annotated file as another PDF), but this action destroys the PDF's table of contents if it had one (unless there has been an update this year to Okular).
Finally, in both cases of Okular for Linux and Adobe for Windows, adding highlights and underlines to text in a PDF involve many more clicks and mouse movement than in Mac Preview (e.g. click and drag to select text, then click an separate toolbar menu to open an annotation menu, then select the specific color gradient of the annotation, the close the menu).
I read (and annotate) a lot of ebooks in PDF format and Mac Preview is one of the main reasons I use Macs, but if Linux or Windows had an as-close-as-possible clone of Mac Preview, that would be really lovely.