When opening a .pdf file in Preview, there is no scroll bar on the right until the window is adjusted

There are several threads that discuss this issue. You can search for preview scroll issues. Here's an example that may help:

https://discussions.apple.com/thread/5791863?answerId=24695407022#24695407022

Just so you know, my default PDF can opener remains set to Preview, though I will use Acrobat Reader when and if it serves my need.

The upside of the Show scroll bars set to always is intuitive with applications. The downside is that any web content that has the CSS overflow:scroll configured will permanently have scrollbars attached to that content. At least, that is the behavior with Safari on Mavericks. Since I do web work too, I have left my scrollbar setting to when scrolling.

I believe the OP issues about resizing PDFs has to do with the default nature of Preview to open PDFs in continuous, rather than single page mode. In the former state, one must always fuss with resizing the Preview window, and in the latter, Preview does what it should do — a single, tightly cropped PDF page. Setting the Single Page preference setting in one document does not make this behavior permanent for subsequent documents.

I made two changes to Preview that open any PDF in Single Page mode, and tightly cropped to that page:

1. Preview Preferences

   PDF: Define 100% scale as: Size on screen equals size on printout

2. Defaults write
   1. Change to ~/Library/Containers/com.apple.Preview/Data/Library/Preferences
   2. defaults write com.apple.Preview kPVPDFDefaultPageViewModeOption 1
      1. Continuous view mode is (0) zero
      2. PDF documents will now default to Single Page mode

Use Acrobat Reader. Providing you have turned off the icon view and launch it in Read mode, Reader will be sized to the document and automatically display a scrollbar.

The constant fussing with Preview to manually adjust, image, and read a PDF continues to decline in appeal. Unfortunately, there is no magic preference setting to fix this issue. Perhaps Apple will address this, but probably not.

Just so you know, my default PDF can opener remains set to Preview, though I will use Acrobat Reader when and if it serves my need.

Right attitude. My point is that there may be not such need for somebody else. As for me.

But my remark was not meant as 'harsh' or 'strict' as you interpreted it, and it was certainly not meant as a critic, it was my opinion only..

Do you have "Show scroll bars: Always" set in System Preferences General?

Hadn't finished my first cup of coffee. Good catch and does paint h/v scrollbars on Preview. One still has to manipulate Preview to document size though.

Do not use Adobe Reader (Viking). Use Preview, at least as good as AR or even better!

Set the "show scroll bar always", as CT has set.

No shortage of opinions here, mine, yours, and others...😉