If the original file is showing as ###, unless you have already made a PDF of it, I think you will be out of luck.
Usually the #### and the ASCII selection prompt tell that OpenOffice cannot understand the file. This can arise because of file corruption, often caused by overhasty closing of a laptop lid, or powering off of a desktop computer, or by program or computer crash, all of which do not permit the file to be written correctly to disk.
The damage is possibly due to over-hasty power-off of computer or closure of laptop lid, before the file housekeeping has been written to disk, or to computer or program crash, or perhaps to Windows forcing an update while you had an OpenOffice file open.
Do not let your computer sleep/hibernate with a document open. When you have formally closed down the computer, wait five or ten seconds before pulling the power lead or closing the laptop lid, to allow the internal buffers of the hard drive flush to disk
As soon as possible try the methods in this tutorial
See
[Tutorial] How to find and un-delete AOO temporary files for detailed instructions on how to
a) use Previous Versions (W7 and later) to recover previous versions of the file (is there something similar on MacOS and Linux?);
b) recover your file as it was when you last opened or saved it, or as it was when it was last saved with AutoRecovery;
c) find previous versions of the file in the folder it is located in, but which have since been deleted;
d) un-delete the temporary files AOO wrote while you were editing the file, and then deleted. This will recover your file as it was when you last opened or you last saved it.
There will be nothing usable in your damaged file - waste no time with it. Try the recovery methods above.
