When working from a different location other than default location you can accidentally send prints to the wrong location. Setting up default printer to "PDF" will prevent his from happening for example when working from home.
How do I print to PDF from MicroStation CONNECT Edition?
Open the Print Dialog
Under Printer and Paper Size, select PDF
Select your Paper Size and make any other modifications you may need.
Once you are done making necessary changes, click on “Print to File…”. The “Save Print As” should open, name the file as necessary and choose folder where you want the .pdf file to reside.
Once completed you can close the print dialog. Note that next time you print, by default MicroStation will remember the last used printer.
How do I print to PDF from MicroStation V8i SS10?
Under File choose Select Bentley Driver.
Choose pdf.pltcfg and click on Open
Once you are done making necessary changes, click on “Print to File…”. The “Save Print As” should open, name the file as necessary and choose folder where you want the .pdf file to reside. Once completed you can close the print dialog. Note that next time you print, by default MicroStation will remember the last used printer.
https://communities.bentley.com/products/microstation/microstation_printing/w/wiki/12895/how-to-print-a-pdf-file-with-levels-and-files-content