How download images from DLSite?

[ppaindx]

Hi I'm new in this forum, i see many users sharing works bougth on DLSite, I wanna purchase some work and sharing here but I find a problem when work expired this work is automatically erased from your library, so i wanna download work before that, some works can download and view with propetary viewer but other works are exclusively for browser view, maybe some user here can teach me how to download comics?