It is not necessary to click ‘Get Tags’ button. This button is left over from the old version of the plugin and is part of the ‘tag generator’ feature.
So, currently there are 3 features which you can use independently.
1. Tag generator tool (old feature that is somewhat deprecated)
2. Field mapper tool
3. Image embedding tool
Image embedding tool does not have an ‘insert tag’ button because it is presumed that you are using some other plugin to insert its image tags into your form.
Let’s say you want to embed the signature from the signature addon plugin into the PDF file. You do not need features #1 and #2. You only need to use feature #3. What you have to do first is insert the [signature] tag into your form (from the signature addon plugin). Then, you have to go to the ‘PDF Form’ tag generator thickbox and use the ‘Embed Image’ button (after selecting the signature CF7 field). Then, you can adjust the selection on the page preview widget to specify where the image should be embedded on the page.
Every time you make changes in the ‘PDF Form’ tag generator thickbox, they are not saved immediately. It is ok to click the X to close the thickbox. Your changes are kept in a temporary hidden input tag on the page. You can reopen the thickbox and still see your changes present there. However, you have to click the main ‘Save’ button of the form if you want your changes to be applied to the contact form.