try doPDF v7...I use it to convert 300dpi images in docx to PDF for publishing - works a treat

Also nitro-pdf and/or Infix both are great but will cost. Also note you're using MAC - look at Scrivener which is more than a PDF converter but does the job

Oh another thing - Word compresses images to 200dpi unless you remove the restriction, therefore loss in resolution. Don't forget to embed your fonts else it will do exactly what you describe.