I would like to report here some considerations I've first post on the VDG section of KDE forum regarding Okular annotation system. As I said in the post, Okular is a great tool, probably the best linux pdf viewer, but for me to reach the perfection it needs a new annotation system. Since the VD group is doing a great job on many components of KDE in this period I hope they could contribute, together with Okular maintainer, to make this software even better.

Original link: (https://forum.kde.org/viewtopic.php?f=285&t=128361&hilit=okular)

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Okular is a great tool, but for me the annotation system is still very poor, and extremely user unfriendly. Here I'll point out some issues in order to stimulate the discussion.

Issues: 
- One can select one annotation tool in a sticky way (so that it is not deactivated after the first use) by double clicking on the annotation tool icon. This is an hidden feature that is not intuitive to use. At least a tooltip should suggest this possibility or maybe the feature can be exposed in a more clever way.

- Inline notes: 
- The text is not entered inline, but a popup to input the text appears. In this way we cannot have a live preview of how the note will look like
- If the rectangle that defines the note we drew is to small, the note is expanded in an unpredictable way which may cover the underlying text. 
- Cannot be resized. This is probably the biggest problem. (connected with the previous one).
- When we double click on the inline note, it's opened as a popup note for editing (but the first time we entered it we need to do it via a different popup dialog box). Should be edited inline.
- Sometimes the inline note rectangle is not expanded and some text is not visible.

- It's not possible to insert text to compile forms fields (I mean in static pdf). One can tweak the inline note to display a transparent background but a frame will be displayed around the text. Moreover since the inline note is not rescalable, it's difficult to match the font required to fill the fields without going above the surrounding text. 

Popup notes:
- The point we click to add a popup notes is assumed to be thee upper left corner of the icon that will be added. I would expect that the point I click is considered the central point of the icon. With the current behaviour the icon is often placed over the text. (See example http://imagebin.ca/v/2G3ed3WI3ueh)
- The note icon size is too large and not configurable.
- The note icon displayed in the configuration dialog of the popup note is different from the icon used in practice (at least on my system).
- I would prefer something like this for popup notes: An icon is diplayed when the note is collapses. When the icon is clicked the popup appears with an arrow-like line pointing to the point where the icon was before (the icon disappears when the popup is open).

Polygons:
- The shape of the polygon (an ellipse for example) is not previewed, so that it's pretty difficult to draw it where we want without going above the surrounding text.

- It's not possible to add a custom image to the pdf. As an example I often would like to add my signature to the pdf. (This would require the image to be rescaled).

Problematic annotations made with different software.
- An odd behaviour I often face is that I find some popup notes that are rendered in okular as very small triangles, so that to open the popup note a super high mouse pointing precision is required. Moreover the "browse mode" pointer has a shape of a hand (and not an arrow) so that it's even more difficult to hit the correct point to open the popup note. I don't exactly know how annotations are stored in the pdf, but okular should be able to process this notes in order to make it easy to open them (somehow the original software must be able to do this I guess). [I need to find an example of this to show you].

- Add ability to draw arrows

- Add the ability to change colour of the highlighter on the fly. Currently we need to configure a new annotation tool for each highlighter colour. The same applies to other tools like shapes.

Another issue is that when we search something, the match is highlighted in yellow making it impossible to find where is the match in an highlighted text. 
A possible solution may be to add a border of a different color to the match and possibly animate the matching with a pulse like animation.
Here's an example from Mendeley:
http://imagebin.ca/v/2G3Z2BJgH7rG

To fix these things a full rethink of the whole annotation interface is required. I hope that the guys in the VDG can devote some time on it, because I think that a tool like a pdf reader is a central application in everyone's daily life, so making it user friendly is very important.

Reproducible: Always