Hmm..it's a beautiful font, what is it..SimSun? But where is this font coming from?

There is an empty place in my heart for these Chinese characters, as they are missing. Legend has it that you could find the Current Value and then look for the font family on the front-end.

CurrentValue[$FrontEnd, {"SystemFonts"}]
Style["中文文字", FontFamily -> "STSong"]
Style["中文文字", FontFamily -> "Songti"]

<|"Controls" -> {FontFamily -> ".AppleSystemUIFont", FontSize -> 13}, "Menu" -> {FontFamily -> ".AppleSystemUIFont", FontSize -> 13}, "Panel" -> {FontFamily -> ".AppleSystemUIFont", FontSize -> 10}, "Tooltip" -> {FontFamily -> ".AppleSystemUIFont", FontSize -> 11}|>

\!(* StyleBox["\<\"中文文字\"\>", StripOnInput->False, FontFamily->"STSong"])

\!(* StyleBox["\<\"中文文字\"\>", StripOnInput->False, FontFamily->"Songti"])

Style["Times, Italic, Bold", FontFamily -> "Times", 
 FontSlant -> "Italic", FontWeight -> "Bold", FontSize -> 24]
Graphics[{FontSize -> 18, 
  Text[Style["Comic Sans MS", FontFamily -> "Comic Sans MS", 
    FontColor -> Red], {0, 0}]}]
SetOptions[EvaluationNotebook[], 
 StyleDefinitions -> 
  Notebook[{Cell[StyleData[StyleDefinitions -> "Default.nb"]], 
    Cell[StyleData["Text"], FontFamily -> "Georgia", FontSize -> 12], 
    Cell[StyleData["Input"], FontFamily -> "Courier New", 
     FontSize -> 12], 
    Cell[StyleData["Output"], FontFamily -> "Arial", FontSize -> 12]}]]
Style["Verdana, Extended, 20", FontFamily -> "Verdana", 
 FontTracking -> "Extended", FontSize -> 20]
SetOptions[$FrontEnd, 
 FontProperties -> {"ScreenResolution" -> 96, 
   "FontAntialiasing" -> True}]

Oh I've got an idea what if you send the .pdf and the Mathematica notebook..then we could try to reproduce and do some debugging. I think if you post some of the output here then I get a notification..I can't tell you how many times that has saved me. I had all these responses I was getting that were getting taken down. And I had this thing where whenever I posted they just immediately took my post down. And now, I'm back. I have returned my dear @Zhenyu Zeng to answer your question, or hopefully we can resume our discussion. And there are lots of fonts for you to try.

We need. Things like $FontFamilies. Or

fonts = $FontFamilies;
DynamicModule[{font = "Arial", size = 12}, 
 Column[{PopupMenu[Dynamic[font], fonts], 
   Slider[Dynamic[size], {6, 72}], 
   Dynamic[Style[font, FontFamily -> font, FontSize -> size]]}]]
sampledFonts = RandomSample[fonts, 9];
Grid[Partition[
  Style[#, FontFamily -> #, FontSize -> 20] & /@ sampledFonts, 3]]

And I know this might seem like a canned response, but what you could do is list all the fonts..and you're using Mathematica 13.2. You could list out all the non-English fonts, those system fonts that Mathematica recognizes. Look for the Chinese fonts in the output. Which one is set as the default in your system settings?

(*ExportString[Style["Export as \
PDF",FontFamily->"Arial",FontSize->20],"PDF"]*)
CurrentValue[$FrontEndSession, "DialogSettings", {"FontChooser", 
  "LastFont"}]
SetOptions[$FrontEnd, DefaultFont -> {"Comic Sans MS", 12}]
TraditionalForm[
 Style[Sin[x]^2 + Cos[x]^2 == 1, FontFamily -> "Comic Sans MS", 
  FontSize -> 18]]

Are you looking? Mathematica loves using the system default font for Chinese characters that may not be explicitly listed under Mathematica's font settings. In this case, displaying all the system fonts recognized by Mathematica might be the leap forward that we need, but it's really about finding the answer we're looking for. Maybe it's your operating system's default fonts for Chinese text. Give us your error messages. The Ruliad untangles a lot of things we thought about philosophy. Some modern AI developments "certainly" help in form. But what we need to do is focus on Windows and Linux. When I saw that you were using Debian 11 that which is a Linux system, I felt a jolt of recognition that yes, you should be able to print more PDFs. Give us your console output! What if you do fc-list :lang=zh ?