To directly address your question, I'd suggest that you shared a link to that file for them to view or download (they won't have edit rights this way and they don't need a Dropbox account to view it).
The other way would be to share a folder directly with them if you want them to have edit rights (assuming that they do have a Dropbox account and the space; i.e.quota, to accommodate the file/folder in question). For example if they have a Dropbox Basic account that comes for free they won't be able to share more than 2GB as this is the space that comes with our free, Basic plan.
Now, kindly note that every folder you create in your Dropbox is private by default. However, a special type of folder you can create is a shared folder. These folders allow you to share files with other Dropbox users. Please note that while it is shared, it can only be accessed by people you explicitly invite.
Additionally, you can decide whether members of the folder are "editors" (meaning they can add, edit, and delete files from the folder) or are "viewers" (meaning they can view files in the folder but not make any changes).
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