Many people write their own license. This is frowned upon as writing a license that does what you want involves subtle issues. Too often the wording used is either ambiguous or people create conditions that conflict with each other. Writing a license that would hold up in court is even harder. Luckily, there are a number of licenses already written that probably do what you want.
Foxit Reader is free for not just reading, but also creating PDFs and collaboration on the files (at least you can with the Windows version; Mac and Linux are more limited). Foxit's MobilePDF apps are on iOS, Android, and Windows Phone. What's more, they support a tech called ConnectedPDF so you can send PDF files and even update them after you send them (thanks be to the cloud).
Copyleft licenses, with the GNU General Public License being the most prominent: the author retains copyright and permits redistribution under the restriction that all such redistribution is licensed under the same license. Additions and modifications by others must also be licensed under the same "copyleft" license whenever they are distributed with part of the original licensed product. This is also known as a viral, protective, or reciprocal license. Due to the restriction on distribution not everyone considers this type of license to be free.
With bought leads, these lists are typically made of potential candidates that have shown interest in related products and services to what your business may offer. So there is a good chance that at least a good chunk of these leads will prove to be successful in the conversion process. With each free sales leads that you work to obtain, there is no guarantee whatsoever that the lead will produce the results you want, and the leads in your inbox will likely be more scarce than the packed list you can purchase.
Mozilla's email client extraordinaire has jumped to version 45, but it still has all the features that made it great: account setup wizards, multiple languages, hundreds of add-ons, a tabbed interface, great search, junk mail and phishing tools, and the option for a personalized email address with your own choice of a domain name. Migration from previous versions is a breeze and worth it if you're on the desktop.
Proprietary software uses restrictive software licences or EULAs and usually does not provide users with the source code. Users are thus legally or technically prevented from changing the software, and this results on reliance on the publisher to provide updates, help, and support. (See also vendor lock-in and abandonware). Users often may not reverse engineer, modify, or redistribute proprietary software. Beyond copyright law, contracts and lack of source code; there could be additional shenanigans keeping users from exercising freedom over a piece of software, such as software patents and digital rights management (more specifically, tivoization).
The right to study and modify a computer program entails that source code—the preferred format for making changes—be made available to users of that program. While this is often called 'access to source code' or 'public availability', the Free Software Foundation recommends against thinking in those terms, because it might give the impression that users have an obligation (as opposed to a right) to give non-users a copy of the program.
Comodo does much more than the built-in option in Windows. As it should, it blocks attacks from outside, and it has a malware detector that's better than some antivirus systems. It also installs the Comodo Dragon hardened security web browser. (Be careful during install, though; nice as it is, it may try to change your browser home page and search engine defaults.)