Aren't pull-up / pull-down options documented for STM32F103?
The information you are looking for is in the manual, but not as obvious as it could be.  The table you mentioned on page 160 contains more info:



As you can see, assuming the pin is configured as an input, the value in the ODR registers is the deciding factor as to whether the pin is pull-up or pull-down.  

You can set and/or clear all these bits at once by writing a 16-bit value to the appropriate GPIOx_ODR register, or you can set/reset them individually by using the GPIOx_BRR and/or GPIOx_BSRR registers.

Interestingly, the same ODR register controls the pin state (high or low) when the pin is configured as an output.

I've found that I can sometimes learn more about the workings of the STM ARM controllers by reading through their Standard Peripheral Libraries than their reference manuals!