Page thumbnails – right or left side of document?

Working on a "fancy PDF viewer".

Was thinking of moving the Page thumbnails to the far right of the page (to clean the design up a bit), but all apps I can recall have the thumbnails on the left side ... always.

To me the thumbnails don't look like a vital feature, I mean there are much more important things that can use that valuable left side of the screen. What am I missing in this case and what are the negative consequences of moving the thumbnail previews to position 2 on the mockup?

Thanks.