I wonder if it's possible to buy a PLEX on a trial account and thus make it active with +30 days gametime. Do I have to pay for a subscription to be able to extend my gametime with PLEX?

last I remember, it was possible unless they changed it

if you're planning to make enough money to buy Plex in 21 days of trial....good luck!:) 

latest PLEX prices are at over 400 mil and you'd need to be a leader of an active corp to make that much in such a short time hehe

or be very very very good at scaming people

PLEX can be used by players regardless of the type of account they have. When you activate a PLEX, the extra time is added to your account immediately. In this respect, PLEX works exactly like a prepaid game time code.

• If you are currently using a Trial account, your account is converted to a paying account and the 30 days are added onto the remaining days left in your trial period.

That's what it reads here:

http://wiki.eveonline.com/en/wiki/30_Day_Concord_Pilot_License_Extension

There are some 60-days trial keys, I think it's possible. PLEX in 21 days would be too damn hard.

Yes it is possible.

I've traded my way to a plex on a trial account before, 400+ mil is possible starting with nothing using only frigates, destroyers or cruisers to transport the goods.  It just requires quite a few hours in the beginning making lists of what various modules, goods, ammo, etc are trading for in the different market hubs to find an item(s) with a fairly small volume, good liquidity and a decent markup. 

Also, with a couple of days worth of training you could run the 1/10 hi sec complexes for faction loot although trial accounts cannot create contracts so you might have trouble getting the isk for the loot.  The 1/10 plexes sometimes drop modules which can be worth up to a 100mil and quite regularly drop 10-20mil modules. Once you work out which to run and  how to run them efficiently you can get several in each hour at off peak times.  This can be a nice little earner for a low skill-point pilot if you can play when the server is quiet but as I say, I'm not sure if there is a workaround for the inability to create contracts so that you can sell these with a trial account. 

Great, thank you guys. Now I must get my hands on some 60-days key. Or I might just take 21-days one and buy one month subscription, then PLEX all the way.