Turning a PDF 4 degrees

[Cornflower]

Fellow user BGM asked how to turn a PDF 4 degrees askew. Here is a way to get that 4 degree detail

Irfanview https://www.portablefreeware.com/index.php?id=49

You have to also install the plugin set because it has the PDF Plugins (it is great--check the PDF subreddit for some other things done with Irfanview with PDF plugin).

Open Irfanview and press B for Batch mode (This has to be done in Batch Mode). Load your PDF and under Batch conversion settings
- Set the Output format to PDF. Under Options, tick "Save all pages from original image". You can add a Page format (eg A4, Letter), but you can also choose "like image"
- tick "Use advanced options and click the Advanced button.

In the Dialogue that opens set the following (the rest should be unticked):
- Fine rotation (3rd column) 4.00 for clockwise, -4.00 for counter-clockwise
- Apply changes to all pages (TIF/PDF saving)

Now Irfanview will save the PDF as image (non-OCR), but I assume that the 4 degree askew means it wasn't in OCR form or didn't need to be OCRed anyway. I have straightened one PDF with this method and then OCRed it, and it worked out decently well, but of course no guarantees.

[Cornflower]

I forgot one thing. As I usually prefer a black background when working with Irfanview, especially with aging eyes, change the background to white. Click on the Options menu and choose Properties (or press P). Under the Viewing settings, change the Main window color to **white**. If you don't, the de-skewed PDF will have black or grey or whatever triangular borders.