Dropbox view only links will do the job, this will allow them to view, comment and download the files. They will not have the ability to modify your files if you do the following.
Share a Dropbox link with view-only access
Sign in to dropbox.com.
Click All files in the left sidebar.
Hover over the file or folder you’d like to share and click the share icon (rectangle with an up arrow).
If a link hasn’t been created, click Create.
If a link has been created, select Can view after Dropbox members with this link, then click Copy link.
The link is copied to your clipboard. You can then paste it into an email, message, or wherever people can access it.
I hope this helps.