First, you should realize that this is more of a general Postgres question, since all Postgres databases can be backup up, whether or not they are PostGIS. If you find you need more detailed answers, you should probably ask this question on dba.SE.
The standard way to back up a Postgres database is the
pg_dump utility. You're question is extremely general, so I'm not going to go into detail on the options. Refer to the docs at https://www.postgresql.org/docs/9.5/static/app-pgdump.html.
There are a large number of Postgres administrative front-ends that include backup/restore features, including open source projects like pgAdmin and proprietary tools like Navicat and RazorSQL. I believe that most (possibly all) of the options you will find will just provide a GUI interface to
pg_restore. Some of them, like Navicat, may also include scheduling, so that you can automate your backups. Many of the proprietary tools support multiple RDMBS, allowing you to manage SQL Server, Oracle, etc., in one interface, and transfer data easily between them.
There is a Postgres-specific open source project named Barman (http://www.pgbarman.org/) which manages your entire Postgres backup strategy, including full and incremental backups (WAL, or Write Ahead Log) to ensure point-in-time recovery. I don't know if this is something you need.
Using pgAdmin instead of
pg_dump has some disadvantages. The dump options of pgAdmin are poorly documented. They all map directly to
pg_dump options, but you have to look through the pgAdmin checkboxes and the
pg_dump command line switches and figure out which is which. In addition, while the dump is running, the entire pgAdmin GUI will become unresponsive.
I tend to use pgAdmin backup for a one-off job, and
pg_dump for anything that needs to be run repeatedly, as you can easily reproduce the job, or use the operating system scheduler (
cron on Linux, Task Scheduler on Windows) to run it as desired.
Since you intend to back up several databases daily, the approach I would recommend is to test your
pg_dump command, schedule it to run daily, and write the file directly to a remote location or to a local folder that will be automatically synced (e.g. a Dropbox folder).