Our son in law loaded Paint onto my PC, and this is what i use to resize pictures.
Pictures have to be resized.one at a time, but they can be decreased or increased,as required.
Mostly I reduce files of about 4 Mb to about 1 Mb so that several can be sent by E mail (My system does not seem to be be able to deal with more than 10-12 Mb at a time ) If the reduction is overdone, it is simple to increase again.
Obviously, if the increase in size is excessive quality suffers, a 1 Mb file won't look good resized to 5 Mb.
1 Mb seems to reproduce quite satisfactorily in a magazine. (I was told that 500 Kb would suffice, and, for a while used this, but finally settled on 1 Mb as the target,.giving good reproduction, and the ability to transmit a reasonable number of images attached to one message..
Howard