Cant able to preview the PDFs inside the Tickets

I would like to suggest two applications for your problem.

• Preview Attachments
• Attachment Manager Plus

If you want the preview feature only, go with the preview attachments app. If you want addition features like downloading the attachment, adding the attachment to reply, filter the format. Go with the Attachment Manager Plus. 

Both app have affordable prices like $1 and $2
 

Preview Attachments Features ($1): https://www.freshworks.com/apps/preview_attachments_1/

• List all the attachment in the ticket sidebar app
• preview attachment (supported formats are PNG, JPG, JPEG, GIF, SVG, MP4, MOV, MP3, PDF, DOC, DOCX, CSV, XLSX, XLS, and ODS.)
• Search by attachment name
• sort (A to Z, latest attachment, oldest)

Attachment Manager Plus Features ($2): https://www.freshworks.com/apps/attachment_manager_plus_1/

• Filter and sort options: Filter search results by type or sort them by name or date.
• Preview without downloading: View attachments directly within Freshdesk / Freshservice without downloading.
• Download flexibility: Download single attachments or all at once for convenience.
• Format support: supports all regular formats such as pdf, docx, doc, ods, csv, svg, png, jpg, jpeg, mp3, mp4, and mov.
• sort (A to Z & latest attachment, oldest)
• File type (pdf, jpeg, png, jpg, etc.): Filter attachments by file type for quicker identification and retrieval.

I hope you go the answer for your solution. 
 

Thank you.

You have this as well 

Freshdesk Attachment Viewer Integration | Freshworks Marketplace