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Hi,
Thank you for posting your query on our forum, let me help you with this.
To resolve this issue,
Here are some possible solutions to ensure the PDF opens on the first page in the SharePoint embeddable file preview:
At first, starts with modifying the embed link by appending #page=1 to ensure the PDF opens on the first page,
and then, clear your browser cache and reload the page, as cached data may affect the viewer.
After the above-mentioned steps,
Try opening the file in different browsers to determine if the issue is browser specific.
Then you need to re-upload the PDF, as this may reset any unintended settings affecting the preview.
Also, do try using OneDrive’s embed viewer instead of SharePoint’s, if possible, to see if it helps in resolving the issue.
I hope this helps.
Best Regards,
Tani | Microsoft Community Moderator