You don't state what part of the country you are in - the rules were different in Scotland until late last year.
You do not need to tag any animals that merely stay on your farm (see later) - so we are only talking about the ones you are thinking about taking to slaughter.
These need to be tagged or slapmarked with your herdmark. The regulations state that for tags this must be "printed or stamped". Defra state that this means pre-printed rather than written, but it is up to your abattoir whether they will accept a handwritten, and whilst it is unliklely that you will be "done" by the authorities, you do run a technical risk that they might use you as a test case.
As for the ones you bought, if in Scotland and before november last year, they could arrive at your holding with no ID at all. In England & Wales, those under 1 year could arrive at your farm with a temporary mark. Those over 1 year (probably your boar and sow, and neglacted sow) should have had either a tag or tatoo with the senders herdmark on the pig. However once on your farm, they do not need any further ID as long as they stay on your farm.