Hello all,
The size of the thumbnails in the Thumbnails pane can be changed by using the Zoom In/Zoom Out commands in the toolbar or Ctrl+Wheel on the mouse, but from what I have found, the size changes linearly, even though there are 98 steps in total. Therefore, the larger the size, the more sluggish the operation feeling becomes.

- The area corresponding to the red frame in this figure was screen-captured for each of the 98 thumbnail sizes
and consolidated into a single figure.
The following figure shows the first page of a PDF-XChange Editor license file displayed at 200% scale on a 4K monitor, with 98 different thumbnail sizes from smallest to largest, captured at each size, and consolidated into one figure. The thumbnail size increases linearly as a straight line can be drawn by drawing an auxiliary line at the upper right corner of the thumbnail.

- PDF-XChange Editor
In Acrobat, on the other hand, the thumbnail size has 26 steps, and the size increases at an accelerated rate. The same procedure as in PDF-XChange Editor was used to capture each of the 26 levels of thumbnails, which were then consolidated into a single figure as shown below. If you draw an auxiliary line at the upper right corner of the thumbnail, you can see that the size of the thumbnail is increasing at an accelerated rate.
In the figure, thumbnail size deviates from the trend of the auxiliary line only in the 26th step, because the Acrobat thumbnail size limit was reached first, before the thumbnail size increased nonlinearly.

- Acrobat Reader
Considering the fact that the zoom factor changes at an accelerated rate when Ctrl+Wheel is used to change the zoom factor in normal page view, it would be more intuitive for the user if the thumbnail size in the Thumbnails pane also changes at an accelerated rate rather than linearly. Also, the 98 steps seem too detailed. If the zoom factor of the thumbnails changes at an accelerated rate, the number of steps would naturally be reduced to a manageable number.
As I pointed out earlier in the following topic, the thumbnail zoom factor in the Thumbnails pane is synced between documents and is also carried over to the next document opened.
- The zoom factor of page thumbnails in Thumbnails pane is carried over from the last document used to the new document
viewtopic.php?t=45791
If you intend to maintain that behavior in the future, it seems to me that you might at least want to make it possible to change the thumbnail zoom level more wisely, as in this request, so that it can be easily returned to the standard zoom level even at high zoom levels, thus preventing any loss of usability.
Thank you for taking the time to read this message.
Best regards,
rakunavi
- PDF-XChange Editor PRO Version: 10.6.0 build 396
- Adobe Acrobat Reader Continuous Release Version 2025.001.20474
- OS Version: Windows 11 Pro / Home 24H2 Build 26100.3775
- PC Model: GMKtec Nucbox M7 Pro with HUION Kamvas Pro 19 / Lenovo IdeaPad C340-15IWL