Exporting Impress presentations to pdf in black and white view

I have a lot of files with .ppt and .pptx extensions. I want to convert these files to .pdf using Impress. Because I want to print the same files, I want to export them as black and white for use less ink. Do I have an option other than printing to file option on the printing window?

for example:
It isnt important but, When I tried to printing with LibreOffice Impress as 4x4 i have some spaces between pages.
But I dont want these spaces between the pages, I want the pages between the spaces. If I had exported this file to pdf and printed it as 4x4 with pdf reader I have this.
But unfortunately In this printing has more gray areas. I have an ink printer and if I print it like this my output will be very wet.

Select menu File > Print.
In the “Print” dialog, click on the “LibreOffice Impress” tab.
In the “Color” area, you can select either “Grayscale” or “Black and white”.

@Hrbrgr Thanks for your answer. I know this way. However, I’m looking for a solution with the “Export” dialog if possible because converting to pdf with the “Print” dialog takes longer than the “Export” dialog. And I have many presentations in pptx format