pdf attachments on outlook got red cross mark. how to resolve this?

@saikrishna_8552 was there an arror message to go along with that red mark? 

If this is only through your Outlook, chances are Outlook is unable to properly access or display the attachment, which can arise from several issues. Outlook relies on external applications to render PDF files. If the PDF reader is faulty or missing, the attachment will fail to display. So, then, make sure that Adobe Acrobat is correctly installed and set as the default PDF app on your system. Second, check your Outlook Trust Center settings; go to File > Options > Trust Center > Trust Center Settings > Attachment Handling, and ensure that PDF attachments are not being blocked. Antivirus or security software might also interfere, so temporarily disabling them for testing purposes can help identify conflicts. Finally, if the issue persists, consider repairing your Outlook installation through the Control Panel's Programs and Features, as corrupted Outlook files can also cause attachment display problems.