11 Column 84 Row LED Matrix MicroController?
There are three common ways to tackle this kind of problem.

1. Shift Registers

As has been noted in the comments using shift registers can give you a huge number of outputs using just a handful of microcontroller IO pins. There are specific LED driving shift registers available that are designed for just this kind of thing, such as the STP16CP05. There are more complex ones, such as the TLC5940 or TLC59116, both of which provide PWM, but that can get in the way of multiplexing the LEDs unless you take great care.

Coupling some "normal" shift registers (74HC595) with some suitable P-channel MOSFETs or PNP transistors as high side switches to drive the rows (anodes), along with a bank of STP16CP05 shift registers as the column sinks (cathodes) could be achieved using just three pins on the microcontroller (clock, data and latch).

For lots of LEDs though this rapidly becomes quite hard for the microcontroller to update fast enough. So: 

2. Think modular

You have already created an 8x8 matrix using 16 pins of a microcontroller. So why not do the same again, multiple times? Have all of them communicating on a bus (SPI, I2C, etc), and send instructions to each module telling it what to display. Each individual module is then responsible for performing the multiplexing and refreshing of the image on its portion of the screen.

There are also dedicated chips designed for this purpose, such as the MAX7219 which can directly drive an 8x8 matrix through an SPI interface.

3. Intelligent LEDs

LEDs such as the WS2812 and similar connect in a chain using a simple serial protocol. You can connect many hundreds of these LEDs together, and often come as pre-manufactured strips sold by the metre. These are an excellent option if you want to create a full-colour display.