Your license for Adobe fonts likely precludes alteration. You need to contact Adobe directly. There are circumstances a foundry may allow the alteration on an individual basis. Good luck.
I am unfamiliar with the transliteration of Hebrew, so I'll let someone else answer that aspect. I would begin with a Google search though.
I believe you are incorrect. I believe Adobe does allow you to alter its fonts for your own use, but you are not allowed to give it to anyone else. I'm sure someone from Adobe will step in and clarify.
There are many tools available to import fonts and alter them. However, it is unlikely that the altered font will be identical to the font you started with. For most people the differences will be minor and acceptable. Programs that may do what you want are Font Lab, Fontographer and Type Tool. These tools can be found at http://www.fontlab.com
With regards to Mike Wenzloff's response in terms of the license for Adobe fonts, unlike many other font foundries, Adobe does not prohibit you from making alterations of a font for your own use, whether changing individual glyphs, adding glyphs, deleting glyphs, changing or adding font metrics, and/or conversions to other font types.
Having said that, modifying a standard font is not a particularly prudent idea unless you contract witht he original font foundry to make such modifications. Why? Virtually all commercial font editing software is lossy, even if you don't change font types. The lossiness often occurs in the hinting since most font editors only retain the font shapes from the original font, not the hinting information.
More importantly, the needs expressed by sammyoziel, the original poster in this thread, are very real yet fairly simple. Effectively, he wants to make the equivalent of compound glyphs. The most common example of this is to portray the sound of the Hebrew letter Chet which is the gutteral h sound, often represented in Western Latin languages using ch. Of course, ch is more commonly used for the actual ch sound as in child.
I've seen two methods of dealing with these Hebrew letters with no Western Latin equivalent. The first is what sammyoziel suggests, putting a dot under the character. The other method is to simply use the underscore. For example, use h to represent the chet sound. That requires no modification to any fonts at all and is probably the simplest and safest way of accomplishing what you need.
If you must use the first method (and I have personally had to do this a number of times), I would most strongly recommend against trying to add glyphs to the font. What Unicode values would you use? How would you key them? And you would end up with a non-standard set of fonts. I would recommend that you simply use two glyphs. In the case of the h with a dot underneath, I would first key the h and then the period character. Custom kern the two glyphs such that the period is centered with the h. Then custom lower the glyph such that it is beneath the h. You may also need to do a custom kerning with the following letter or perhaps, insert an extra non-breaking space (see which space width works best) after the period.
Instead of a period, why not use the Unicode U+0323, "Combining Dot Below," even if this requires borrowing it from another typeface? Unicode stopped adding letter-plus-diacritic combinations after only a few dotted consonants, presumably because the possible combinations seemed to approach infinity: instead, Unicode offers combining accents, which can be positioned properly via Opentype features. I'm not sure any current fonts or software fully implement these yet, but the first time I put a combining dot below after a "t" (in Times New Roman with InDesign) it blew me away; and it works for "h", too. Today, a Times NR underdot after a Minion "h" still needs kerning by hand, but if someone comes back to the file a few years hence the intent will be obvious and precise positioning might be a matter of updating the font and ditching the custom kerning. And then there's searchability...