generate thumbnail as a file to import in other software

I need to create a combination of pdf preview an get them togheter.

Actually i have to open the pdf in acrobat and take a screenshot of them, after that i import that screenshot to excel to create an easy combination of that screenshot togheter with other screenshots. Finally a export to pdf for sharing it with colleagues.

My question is if i have already the files preview from bridge avaiable i will import them into excel and combine for my use. How to generate thumbnails files?

I looked into cache folder but it is empty