Update synctex documentation

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

doc/man/_options.txt

@@ -28,7 +28,13 @@
 
 --synctex-forward=input
   Jump to the given position. The switch expects the same format as specified
-  for synctex's view -i.
+  for synctex's view -i. If no instance is running for the specified document,
+  a new instance will be launched (only if --synctex-pid is not specified).
+
+--synctex-pid=pid
+  Instead of looking for an instance having the correct file opened, try only
+  the instance with the given PID. Note that if the given PID does not have the
+  correct file open or does not exist, no new instance will be spanned.
 
 --fork
   Fork into background

doc/man/_synctex.txt

@@ -1,6 +1,6 @@
 Both synctex forward and backwards synchronization are supported by zathura, To
-enable synctex forward synchronization, please look at the *--syntex* and
-*--synctex-editor* options. zathura will also emit a signal via the D-Bus
+enable synctex forward synchronization, please look at the *--synctex-forward*
+and *--synctex-editor* options. zathura will also emit a signal via the D-Bus
 interface. To support synctex backwards synchronization, zathura provides a
 D-Bus interface that can be called by the editor. For convince zathura also
 knows how to parse the output of the *synctex view* command. It is enough to

doc/man/_synopsis.txt

@@ -1,2 +1,3 @@
 zathura [-e XID] [-c PATH] [-d PATH] [-p PATH] [-w PASSWORD] [-P NUMBER]
-[--fork] [-l LEVEL] [-s] [-x CMD] [--synctex-forward INPUT] <files>
+[--fork] [-l LEVEL] [-s] [-x CMD] [--synctex-forward INPUT] [--synctex-pid PID]
+<files>