How much of the "information" in the signal are you trying to preserve? If you just have an essentially digital signal, it might be easy to process it through an "RS232" receiver, e.g. MC1489 or the like, which will translate it into a digital TTL-compatible signal, thereby skipping the business of shifting the levels in analog format. If there's information aside from the rate, however, you probably do want to shift it, and adding a DC bias to it quite straightforward.

If, by "send it to a processor", you mean to convert it to digitized format, you have other options, e.g. using a converter that processes voltage in that range into unipolar digital format. Once in digital format, you have multiple options.

RE