Issue Summary
When exporting PDF files on the space level using the "custom" option to select specific pages, the PDF export is very slow despite selecting only 1 page with not a lot of content.
Below is an example of an export with space that only has a few pages containing just a few text:

In some cases, it goes all the way up to 1 hour or more.
The issue only seems to impact the custom export. Page-level exports are performing better.
Steps to Reproduce
- Export a space using the "custom" option
- Select one or two small pages
- Start the export
Expected Results
PDF export finishes in a reasonable amount of time
Actual Results
PDF export takes much longer in relation to the amount of content within the selected pages to be exported
Workaround
Use page-level exports
Unfortunatly, the suggested Workaround is not suitable, since it doesn't allow for selection of Pages which need to be exported, it only converts the actual site you are on.