The following code uses the itoa() function to convert the variable "packetnum" into a human-readable ASCII character array (C-string) and sends it to the receiver.
char radiopacket[10] = {0};
itoa(packetnum, radiopacket, 10);
rf95.send((uint8_t *)radiopacket, strlen(radiopacket));
You can do the same for several integer variables, separated by commas, using the snprintf() function. For example:
char radiopacket[30] = {0}; //make sure this is large enough
snprintf(radiopacket,sizeof(radiopacket),"%d,%d,%d",pressure, humidity, temperature); //assuming p,h,t are integers
rf95.send((uint8_t *)radiopacket, strlen(radiopacket));