PDF icon after unzipping changes

Question

I was recently sent a PDF file obtained by scanning some paper sheets with the software CamScanner (File.pdf). I noticed that the top right corner of the Desktop icon was not fully bent and it looks like only the first page of the document had been angled (see photo below). Instead, if I compress the file and open it the corner is now fully bent.

At the same time, the left-hand black strip on the icon disappears.

I'm assuming there's something changing in the format or encoding but I have no idea what it is happening to the file. Does anyone know what this means?

I'm working on a macOS Ventura 13.2.1 if that helps in any way. Thanks!

EDIT: The original file is not accepted for submission in the TurnitIn online platform while the other one is, so something in the metadata must have changed as pointed by @Xenonite. Still, the change in the black strip perhaps is the most obvious difference and I don't know what that represents.

Answer 1

It is possible that the differences you are seeing in the PDF file icon are due to changes in the file's metadata or thumbnail preview. When a file is compressed, its metadata and thumbnail preview are typically updated to reflect the new file size and format.

In the case of your PDF file, it's possible that the compression process caused the metadata or thumbnail preview to be updated, resulting in the changes you observed in the file icon. However, the actual content of the PDF file should not be affected by the compression process.

It's also possible that the differences you observed in the file icon are simply due to visual artifacts or inconsistencies in how the icon is displayed by your operating system. This can sometimes occur when working with files that were created or edited on different platforms or software applications.

If you want to verify that the content of the PDF file has not been affected by the compression process, you can try opening both the original and compressed versions of the file and comparing them side-by-side. If the content appears identical, then it's likely that the differences you observed in the file icon are simply due to metadata or display issues.

Answer 2

Some time ago, Apple changed the preview icon for PDFs, so that multi-page PDFs show a 'binder' on the left edge, and pages shown behind the corner fold of the first page.

Note that content from page 2 will actually show where the corner fold is.

A single page PDF has no binder and no pages behind the fold.

Why you get the single-page icon for the second file (if it's identical), I cannot explain. It may simply be that after un-zipping, the file is still being processed by Spotlight/QuickLook.