You can decide to reduce the data necessary to print your document. The settings can be defined differently for printing directly to the printer or for printing to a file.
Choose Tools - Options - LibreOffice - Print.
Click one of the following settings options:
Printer - to define options for reducing data while printing directly to a printer
Print to file - to define options for reducing data while printing to a file
Select any combination of the four options, then click OK.
All documents that you print from now on will use the changed options.
Print your document.
You can reduce data for transparency, for gradients, or for bitmaps. When you reduce the data, on many printers you will not see a reduction of printing quality. But the printing time is substantially shorter, and when you print to a file, the file size is much smaller.