Ask question about Altera FPGA's PLL

The PLL output goes through a global buffer, and the internal fanout of a global buffer is unlimited.

If you refer to the internal clock distribution, read about global clock nets in the respective device handbook. General, it won't be a problem to supply it to all lgic cells in your FPGA. If you mean the external clock output, read about the specification for the I/O standard of your choice.