Markers Loading Time

I am using Storyline to create a map providing details of contacts all over the world. Initially a map of the world appears. The user then selects one of eight regions. Markers appear showing the location of each contact. If a contact is selected, the marker box contains a hyperlink to access a PDF containing detailed information. One region has a lot of contacts (about 30) whereas other only have two or three.

Initially I created a slide with 8 layers (plus the base layer) as I thought this would be better as there is no moving between slides. The map took a long time to load and was very slow to appear. So I then changed things so that I had an initial map slide and eight other slides. The region with 30 markers is very slow to appear, and the whole map is quite sluggish, presumably because users can select the slides in any order.

I have also made sure that the PDFs are not stored in the same folder as the Storyline files, in case this makes a difference.

Does anyone have any suggestions or "best practices" as to how I can make the make react more quickly?

Thanks!