I think you may have misunderstood, or I communicated badly. If you use anything other than the standard (base-14) fonts with a form field, then Acrobat will embed the entire font in the document, resulting in a corresponding increase in file size The built-in fonts that will prevent this are shown below:
In other words, you don't need to buy anything. The fonts shown above - or suitable replacements - are guaranteed to be available for use with a compliant PDF viewer.
Here's a list of the base-14 fonts and what Acrobat/Reader actually use, at least with Acrobat 9:
Base-14 font: Used font (Acrobat 9)
Zapf Dingbats: AdobePiStd (embedded subset)
Neglecting the form fields, one font are so does not usually increase file size much, particularly if it is a subset font. Some folks like to use almost as many fonts as they have on their computer to be fancy and the file size becomes huge, or they have embedded no fonts and others can't read the file. So just try to not use more fonts than you need and let the form fields use the defaults. For the fonts you use, you should embed them as subset fonts. (just check the document properties on the produced PDF)
Nobody ever claimed they are the best font to look at. Their importance here is that Helvetica is one of the fonts chosen for special treatment when PDF was designed 20 years ago, so that it always works in a PDF. (That is, it is the job of every PDF reader to make sure you see something reasonable - perhaps Helvetica, perhaps Arial, anyway a similar Sans Serif font).
Contrary to misinformation there is nothing special about Arial in a PDF.
Nobody's saying Arial/Helvetica are the best for everything, but they're the default sans-serif typefaces (I'm not getting into a discussion about the derivation of Arial from Helvetica and who stole what, those conversations tend to go on until blood is drawn). A page of text in a novel should be serif (e.g. Times) so you can pattern-scan per word, but for headline and small blocks of text (such as form fields) a sans-serif font is more legible thanks to the increased X-height, even though you have to letter-scan when reading it.
In terms of embedding fonts for forms, you should never go anywhere near Arial unless you absolutely have to support full Unicode in a text field; it's by far the largest font file in the Western set.
This may need to be be moved to another section:
When I create PDF usually with MS word But could be by other means.
When Look at File size its rather large. I then go into Optimizer Window and there are multiple copies of the same Font that I have to remove.
here is but one example:
Sometimes its not subsets. There should be one copy and onecopy only of each type
Plain Bold italic and so on.
This has strayed a bit from the original topic, which was started in a different thread here, so I'll add a bit more background info for the benefit of others who may come across this thread in the future...
As this list above shows, Acrobat/Reader actually use a version of Arial when Helvetica is selected for a form field. I often see that a form author will choose Arial, as opposed to Helvetica, for some unknown reason. All it does is cause an unnecessary increase in file size since the entire font has to be included in the PDF. The reason the entire font gets included is so that any characters it contains are available when the form user (or some other process) fills-in the fields. Since Arial is used when either Helvetica or Arial is selected, there is little reason to select Arial.
Well having up to half a dozen copies of the same font doesn't affect readability. The only thing it affects is the size of the PDF. There are reason for PDF to be large Type and size of Graphics, and Meta Data. But Fonts usually re the number one killer.
I better let this go. We have stray from the subject. And the tight cubby holes we are now put in don't lend well into discussing other parts of an issue.