A PDF that scrolls sideways instead of down is almost always a viewer setting issue rather than a problem with the file itself. The document is fine โ the viewer is in a scroll mode that shows pages side by side rather than stacked vertically. A few clicks fix it in most viewers.
How PDF Viewers Control Scroll Direction
PDF viewers offer several page layout modes that control how pages are arranged on screen. Single Page shows one page at a time with no scrolling between pages. Continuous Vertical (the default in most viewers) stacks pages top to bottom and lets you scroll down through the document. Continuous Horizontal arranges pages left to right, producing the sideways scrolling you're experiencing. Two-Page View shows two pages side by side, which can also cause apparent horizontal movement when navigating.
The layout mode is a viewer preference, not a property of the PDF file itself. Changing the mode in your viewer fixes the display without altering the document.
Fixing It in Adobe Reader
In Adobe Reader and Acrobat, the page layout setting is in the View menu. Go to View โ Page Display and look for the scroll direction options. Select "Enable Scrolling" for continuous vertical scrolling, or "Single Page" if you want to navigate page by page. The keyboard shortcut Ctrl+Shift+H toggles between horizontal and vertical continuous scrolling in some versions.
Fixing It in a Browser Viewer
Browser-based PDF viewers (Chrome, Firefox, Edge) usually have a settings or view menu accessible through an icon in the PDF toolbar. Look for a page layout or scrolling option. Chrome's built-in viewer has a settings icon (gear or three dots) where you can switch between single page, multi-page vertical, and other layouts. If the browser viewer doesn't offer the layout you want, download the file and open it in a dedicated desktop viewer.
When the PDF Itself Sets the Initial View
PDFs can include instructions that tell the viewer how to display them on opening โ the initial zoom level, the page layout mode, and whether to show the bookmarks panel. If a PDF was created with a horizontal scroll as its specified initial view, it will open that way in viewers that respect those settings, even if the viewer's default is vertical.
In Acrobat Pro, you can see and change the initial view settings via File โ Properties โ Initial View. Setting the Page Layout to "Continuous" and saving the file makes it open in vertical scroll mode for all viewers that respect initial view preferences. For PDFs you received and can't edit, changing the viewer's display mode overrides the file's initial view setting.
When the PDF Pages Are Landscape Orientation
A landscape-oriented PDF (wider than tall) displayed in a continuous vertical layout naturally requires horizontal scrolling if the page is too wide to fit the screen at a readable zoom level. This isn't a layout mode problem โ it's a zoom and fit issue.
Switching to "Fit Page" or "Fit Width" zoom shows the entire page width within the window without horizontal scrolling. "Fit Page" shows the complete page; "Fit Width" matches the window width to the page width so the content is as large as possible without requiring side scrolling. Both options are typically in the View menu or the zoom dropdown in the toolbar.
Fixing the File If You Need to Send It to Others
If the PDF was created with horizontal initial view settings and you want to change this before sharing, you have two options. If you have the source document, re-export without specifying a non-standard initial view โ most export processes default to vertical continuous scroll. If you have the PDF and Acrobat Pro, change the initial view settings and save. Running the PDF through a PDF Editor or optimization tool often resets the initial view to standard defaults as a side effect of rebuilding the file structure.