Installing this package via NonGNU ELPA or MELPA or any of the other package managers is straightforward and should just work! You should not require any manual changes. The documentation below is only if you are installing from source, or for troubleshooting / debugging purposes.
pdf-tools requires a server
epdfinfo to run against, which it will try to compile and build when it is activated for the first time. The following steps need to be followed in this order, to install