Are there any legal risk associated with accessing resources from a server by its public url? [closed]

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http://serverfault.com – I have a list of urls with some static-contents of my interest (pdf files and images). Those urls are not intended to be accessible to everyone, i guess the owners just think that no one knows the specific path of resources, so they are not protected by password or by any other kind of server side security, and if I submit a get request I just get the requested content. Are there any legal issues submitting requests to those urls using a personal computer and without sharing the resources i get with anyone? (HowTos)