XLSX is Microsoft Excel OOXML document format. This command line showing how to convert multiple XLSX into PDF. This article is intended for everyone to be able to convert Microsoft Excel into PDF document in GNU/Linux system. This article is also a companion of converting Excel to Calc article.
soffice --headless --convert-to pdf *.xlsx
Important note: close all LibreOffice windows before running this command, otherwise it won't work.
A sample result shown below for 2016 Monthly Calendar (left = XLSX, right = PDF):