Is there a way to compress pdf file?

I am generating my PDF document (thesis) with LuaLaTeX. Almost all of my figures are made with the pgfplots package and do not exceed 40 kB. The document is 178 pages. The size of this document is 34 MB. It is to large to upload to our library server.

Even if I exclude all non-PDF images the size does not decrease much. It decreased on the size of png images I'm using.

Is there a way to reduce the quality of the document and compress it? For example: compress all figures...