Hi guys.. I;ve wondered for some time, whether ont to words such as "PC's" and "PDA's" actally require apostrophe's? I often see them wrriten as PDAs and PCs.

Both are acceptable (to some/many?) unfortunately, but the reasonable one IMO is the one with PCs and PDAs.
Well, let's discuss what apostrophes are for:

Showing possession (That is Samantha's pencil.)

Showing that letters are missing...used in a contraction (can't, don't, won't)

PCs is therefore correct. You just add an "s" to show plurality. Adding an apostrophe there is wrong unless something belongs to that PC. (Is it the PC's mouse...yeah, that's awkward and I'd probably never say that, but I can't think of a good example.)

Okay, yes, there are missing letters (ersonal and omputer), but you're not going to write P''''''C'''''''s, so why write PC's? The missing letters thing is really only for contractions as shown above.
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ytsirkbut you're not going to write P''C''s, so why write PC's?
Well, I tried to insert an apostrophe for every missing letter, but it got edited out when I posted it...so now it doesn't make much sense. Oh well. I think you get the point though.
This is a commonly asked question. The references I looked up all said you shouldn't use the apostrophe in this case. There is an exception when you try to pluralize the English alphabets. For example,
Mind your p's and q's.
Cross your t's and dot your i's.
The tendency nowadays is to add a simple -s when pluralising abbreviations, letters of the alphabet, symbols, numerals, and so on, though -'s is still fairly common. So the abbreviations MP and VIP would preferably be pluralised as MPs and VIPs; similarly words not usually used as nouns: whys and wherefores. (The Right Word at the Right Time)
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Back in the old days -- old, but still within living memory! -- the apostrophe was used to create the plural of such entities as PC and PDA. The more recent trend is to omit the apostrophe. You will still see both. Since I'm "old-school", you will see me using PC's as the plural of PC, for example. (Old habits die hard.) Emotion: smile