Screen2PDF

Screen2PDF is a lightweight application that lets you capture a portion of the screen, convert the resulting image into a PDF file and save it to your computer without significant efforts.

No installation needed

Since it is portable, this application doesn't require you to install it on your computer, as simply extracting the archive it comes in and launching its executable grants you full access to its capabilities.
More so, it doesn't tamper with any of your Windows registry entries, can be run from removable storage media such as USB flash drives and external HDDs and doesn't create additional files or folders on your PC without your explicit permission.

Lacks a standard interface

Unlike other similar apps, Screen2PDF doesn't provide you with a standard user interface or system tray icon, which might feel a little inconvenient at times. It is also impossible to call any of this application's functions.
The only sign that the application is running is that your cursor briefly changes into a cross-shaped one and click-dragging it enables you to draw a selection box on your screen.

Takes screenshots and saves them as PDFs

This application can help you save stills of your screen and convert them into PDF files on your computer without considerable efforts. The only steps you need to take is select the desired area that you want to capture and specify a destination folder for the PDF file to be saved in.
As stated before, you cannot call the app's functions through a hotkey or minimize it to tray and access it from there. Therefore, the capture box appears shortly after launching the executable. To avoid the app's root directory window or its icon appear into your screenshots, you can use the ALT + Tab key combination, as the selection box is launched as a separate process. Although this is an inconvenience, you can use the workaround mentioned above.

Lightweight screenshot to PDF conversion tool

To wrap it up, Screen2PDF is a portable application that can help you take screenshots, convert them to PDFs and save the resulting file to your computer. It lacks a standard interface and doesn't let you call its functions by using hotkeys or minimize the process to the tray, which can be disconcerting for some users.