DASHED LINE

Hi @VALERIA25412625hpg1,

We are sorry to hear about the trouble you are facing. Would you mind sharing a few details along with the ones asked above by John Mensinger & Mohammad Harb:

• The exact version of Illustrator & OS
• Screenshot of the PDF export settings
• Was this file exporting correctly in the previous version, or is this a new file?
• Is this happening with the specific document? If yes, would you mind sharing the document with us? You can upload it to the Creative Cloud (https://helpx.adobe.com/in/creative-cloud/help/share.html) and share the download link. We'll check at our end.

We are here to help. We just need more info.

Thanks & Regards,

Anshul Saini

Posting before/after screenshots would surely help.

Are the lines Stokes or Fills ? if stroke, what is the width of the stroke ? 

please post a screenshot.