Serial / auto increment data type

I am just beginning to teach myself Postgresql and Access.  I notice that PG has the "serial" type of field which increments automatically.   I notice that when I do external links in Access through ODBC, that Access wants a field or fields which will be unique.

 

Here is my question.  Would I be wise to define each and ever table with a serial id, so that I may always be guaranteed something uniqe, to satisfy Access.   It seems to me like no harm can be done, since if you dont need the serial id, you dont need it, but it is always there if you do need it, and it is harder to add such a field down the line, after the fact.

 

Thanks!