How are programs split up into pages in Memory Paging?
The program is not really split up into pages. The program is unaware of where it lands in physical memory. This is all the essence of paging.
For example, if you take Linux on x86 CPUs and the C++ language, you will have the compiler generating machine code which will be linked into a final executable which has a .ELF extension.
ELF files support virtual addresses. ELF files specify the virtual addresses at which the code is going to land. The linker or compiler is going to write the starting virtual address at which the code is going to land. The default virtual address is 0x400000 with ld and g++.
So basically, the ELF executable specifies where the program lands in virtual memory. Since the default virtual address is always 0x400000, then a lot of programs will have that starting virtual address. The kernel thus creates page tables for each process (each executable that you start). These processes will land at different places in memory even if they all have the same virtual address. This is due to the fact that they have different page tables.
In fact Linux holds a page struct for every physical page in the system. This takes up quite some space and there have been discussion to change this pattern. I don't know if it is yet done. The page struct allows the kernel to map all physical pages to know what every page is used for.
So when you start an executable/process the kernel determines what physical pages are available and set up the page tables for that process so that virtual address 0x400000 lands there once translated by the MMU.
The JMP 8 instruction will be translated by the MMU before being placed on the address bus. So the 8 is a virtual address. This virtual address is determined by the compiler and the linker.
There are 2 different kinds of JMPs. Relative JMPs and absolute JMPs (far JMPs). Relative JMPs are calculated as an offset from the current position in the code. Far JMPs in the meantime are calculated as absolute address. They contain a virtual address where the JMP should go. They can JMP anywhere in RAM.
For example,
label:
jmp label

is a relative JMP, while
jmp 0x8000

is an absolute JMP. These jumps are calculated by the compiler and linker. The compiler places the functions you call from main at different positions in the code that it places in the relative JMPs. Far JMPs are mostly used in operating-system development.
The linker plays the role of linking several files. So you have a symbol section in the ELF file. This symbol section contains entries which associate each symbol with an address. I'm not totally aware since I never wrote an ELF interpreter. What I can tell is that the address is the address of the beginning of something like a variable or mostly functions. What happens is that the linker takes the symbol and checks it against other object files you included in the linking command. If it finds the symbol in another file, it places the address of the code in the relative JMP to tell the code where to JMP to get to that function. That is why it is called a linker, because it resolves links. This is why you have to include header files in C++. You tell the linker where to find these other symbols (functions, variables, classes).