How can I stop post scan processes?

In Windows the preset for scanning with Acrobat can be configured.
Choose File > Create PDF > From Scanner > Configure Presets.
Look over what is there. Perhaps a setting to de-select what you do not want/need?

If you are using the native scanner user interface instead of the Acrobat user interface, you are presented with the device's
windows/dialogs. The scanner's documentation should describe what configurations options are available and their effect.

Using Adobe's functionality, for image setting processing do you want automatic, automatic/aggressive, or custom?
With custom you'll be able to configure filtering for deskew, background removal, edge shadow removal, despeckle, descreen and halo removal.
Look over compression as well. There will be choices for color/grayscale and monochrome.
See what the Acrobat Help discusses for these if any are a (?).

Something else to look over in Acrobat.
Go to the Preferences. Look over what is there for Convert to PDF from TIFF.

Be well...

I turned off everything except deskew but it didn't change much. With Acrobat Pro 7.0, when I scanned a black and white text document, it kind of looked like a photograph, possibly due to lack of background removal but the letters were clearer and more visible. From 8.0, it removed the background but it retouched the text too much so that it looks like as if it's sharpened too much. Sometimes I see this change happening during the post-scan process. I see it usually during when it says "image processing" on the bottom right with the thin blue bar status. I hate it.

Acrobats tools are geared to convert scanned PDF files to OCR - you should be able to scan to PDF without any image processing.

what scanner and what scanner driver are you using ?

HP Officejet 5610. It's Acrobat that causing this. When I scan from Photoshop, it's fine.

no, that is not really true "t's Acrobat that causing this" - photoshop does not offer multipage scanning and many other "Optimize Scanned PDF" features. Something is set as some default and perhaps that needs to be "un-set" .

I have Acro 9 at my work - will see what is available, but I suspect this really is a preference as daka630 suggest.

Well, that's what I meant when I said "Acrobat that's causing this", some configuration in Acrobat.

while different versions of acrobat may install differently (with different defaults) - as someone who actively is a developer and marketing "paper to PDF" solutions, my experience is that Acrobat does not automatically do anything related to images (TIFF or JPEG) that it converts into PDF files.

Typically, this sort of thing would be controlled within the TWAIN driver setting, and I can't begin to tell you where (or if) you have access to the twain driver settings in Acrobat.

Lets look at your workflow ---

http://www.adobe.com/designcenter/acrobat/articles/acr7ct_createpdf.php

is it like that ?

Can I assume that while in Acrobat, you are going under the File Menu and selecting "Create PDF" and then selecting "From Scaner" ?

When the "Create PDF from Sacnner" dialog box is revealed, is there an active "Image Settings" button down near the left bottom of the dialog box ?

When You click on that, can you change the settings ?

All of our customers either use a built in scanner driver that we custom build into the application (in the case of ELAN-GMK Proofer suite, Capture and most of the other products) - or, we build a special plug-in the import TIF and JPEG image file, using Irfan View

http://www.irfanview.com/

then, you can convert the images as you wish.

I work with IoFlex. They provide high end tools as a suite of Acrobat Plug-ins for the book scanning vertical, where they have a printed book and the user wants to get rid of screening and other artifacts.

http://www.ioflex.com/imagecompare/Compare.asp?Image=00010.tif&Loc=1x6