Try using shrinkpdf to compress your pdf file

And this post: How to run shell script file using nodejs?

Using ghostscript4js:

gs.executeSync('gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=out.pdf in.pdf')

See this answer for various options.

Needs to have ghostscript installed on the host system though.

This can be easily achieved with ConvertAPI NodeJS library:

var convertapi = require('convertapi')('<YOUR SECRET HERE>');
convertapi.convert('compress', {
File: '/path/to/my_file.pdf'
}, 'pdf').then(function(result) {
     result.saveFiles('/path/to/dir');
});

The compression level can be adjusted by specifying the image compression algorithms and quality. You can also remove redundant objects from the PDF including fonts, bookmarks, annotations, forms, page labels, article threads, tagged information, page thumbnails, layers, duplicates, piece information dictionaries like Adobe Illustrator or Photoshop private data, etc.

You can find a complete list of compression parameters here: and the auto-generated code snippet at the bottom of the page.

Disclaimer: I work for the vendor of the library.