show the file as image

I'm developing a site with node js, it has upload / download files like (pdf, slide, docx, etc.). And able to show the files that were uploaded. Now I have a problem showing it in the view (I wanted it to show the image of the 1st page of the file in the view) as in the slideshare site. Someone could give a cami nho? I tried to search but I did not find it. Thank you.