Tại sao các tệp PDF được tạo bởi Microsoft Word quá lớn?

I created a simple Microsoft Word document containing just this sentence, nothing else:

This is a small document.

Then I saved the document as.docx and.pdf files. Here are the file sizes:

• .docx: 12 kB
• .pdf: 89 kB

The difference between the two files is huge (technically) and it really bothers me when documents that are mostly textual in nature are just tens of kB in.docx format, but are hundreds of kB in size when converted to PDF files. What is so inefficient about the PDF format? Is it just Microsoft Word using some terrible output algorithm?

By the way, the PDF output settings on my Microsoft Office installation are set to create the smallest files possible:

If you open the PDF file in Notepad++, you will find:

If you want to prevent fonts from being embedded in a PDF file, then make sure your Microsoft Word documents make use of one of the 14 standard typefaces available in PDF viewers (Source: Wikipedia).

• Times New Roman > Times (v3) (in regular, italic, bold, and bold italic)
• Courier New > Courier (in regular, oblique, bold, and bold oblique)
• Arial > Helvetica (v3) (in regular, oblique, bold, and bold oblique)
• Symbol > Symbol
• Wingdings > Zapf Dingbats