Bug: I have a 30-page PDF file that, when emailed out, some recipients see a PDF file with only the first page (although the file size is correct).

The final 30-page PDF was merged from 3 PDF files:
1. File #1: 1 page, converted from Microsoft Word 365 using its native PDF exporter
2. File #2: 2 pages, converted from Microsoft Word 365 using its native PDF exporter
3. File #3: 27 pages, came from an external party who said it was converted from Microsoft PowerPoint 365

The scenarios:
1. Scenario 1: emailed out from Outlook 365 to Gmail (and to some Outlook users), the User can only view the first page (even though the file size is correct)
2. Scenario 2: used an online tool to "compress" the PDF, then the file can be sent correctly ... i.e. the recepient can view all pages

Upon investigation of the PDF properties:
1. all files mentioned above were PDF Version 1.7 (Acrobat 8.x)
2. Scenario 2 file is missing the XMP Media Management Properties metadata compared to Scenario 1 file. Furthermore, when comparing File #1, File #2, File #3, and Scenario 1, Scenario 2 files, after merging the metadata became a mix from File #1 #2 #3 ... while Scenario 2 mainly has the XMP Media Management Properties removed