In short, yes. It does matter.
Seeking permission often reduces risk if it is unclear if the proposed reproduction or public distribution or use is a fair use or otherwise permitted under copyright law, but can be unnecessary when there is a clear exception under copyright law or the proposed use is clearly a fair use.
It is sometimes best to obtain permission, particularly for images, sound recordings, videos, or other media, and even scholarly articles before posting on a website. If you are going to ask for permission, then you need to be prepared not to proceed if permission is denied (or if you do not want to pay the fee requested for the permission.) because it might more likely to result in a dispute should the copyright owner learn that the you went ahead after being denied permission.
One should generally obtain permission to use copyrighted materials for protected uses including reposting and distributing outside of fair use cases.