Tested here with a 12-page PDF, and it worked fine. Share your file and someone will check it out...
Upload the file/s to a free server, such as Google Drive or MS OneDrive, right-click the link and Share or Copy. Copy the result and paste it here or to me in a Private Message via the mail envelope in the top-right corner of this forum. When using Google Drive, click SHARE | SHARE and change "restricted" to "anyone with link can view.**
In the interim, try these steps in PicoPDF:
Check page thumbnails
- Look for a Pages or Thumbnails panel (often on the left).
- If you can see multiple page thumbnails there, then PicoPDF is loading them but your main view may be zoomed or scrolled so that you only see page 1. Scroll using the scroll bar or Page Down / arrow keys.
Use page navigation controls
Use Next Page / Previous Page buttons, or type a page number into the page box if there is one.
If navigation jumps but the display stays on page 1, the file may be triggering a bug in PicoPDF’s renderer.
Test with another multi‑page PDF
Open a different multi‑page PDF in PicoPDF.
If that one shows all pages, the issue is with the specific file (often complex objects, special optimization, or “Fast Web View” style settings that simpler viewers mishandle). Adobe is more tolerant of these features, which explains why it works there.
Re‑save the PDF from Adobe
In Adobe, do File → Save As, and save a new copy (optionally as “Reduced Size PDF” or “Optimized PDF” with simpler settings).
Open that new copy in PicoPDF and see if all pages appear. This often strips advanced features that confuse simpler viewers.
Update or reinstall PicoPDF