How to Merge PDF With Different Sizes
Merging PDFs with different page sizes — mixing A4 reports, Letter-sized contracts, and landscape charts into one document — often produces an inconsistent viewing experience with pages jumping between dimensions. SublimePDF's merge API handles mixed-size merges and offers options to normalize, scale, or preserve original page sizes for a polished final document.
Follow the step-by-step instructions below, then use the free tool directly — no registration or download required.
Open Tool →How to Merge PDF With Different Sizes — Step by Step
Upload your mixed-size PDFs
POST all files to /api/v1/merge as multipart/form-data. SublimePDF automatically detects each page's dimensions. The merge proceeds regardless of size differences.
Choose a page size strategy
Set the 'pageSizeMode' option: 'preserve' keeps each page at its original size (default), 'normalize' scales all pages to a target size, or 'largest' uses the largest page size as the target. Each has tradeoffs between fidelity and consistency.
Set the target size for normalization
When using 'normalize' mode, specify the target: { "pageSizeMode": "normalize", "targetSize": "A4" }. All pages are scaled proportionally to fit the target dimensions. Content is centered with margins if the aspect ratio differs.
Handle orientation mismatches
Set 'autoRotate': true to automatically rotate landscape pages to portrait (or vice versa) when normalizing to a single orientation. Set it to false to preserve each page's original orientation.
Review the merged output
Download and scroll through the merged PDF, paying attention to page transitions. Check that no content was clipped during scaling and that text remains legible on resized pages.
Pro Tips
- 💡 The 'preserve' mode is safest when content integrity matters more than visual consistency — each page retains its exact original appearance.
- 💡 When normalizing to A4, Letter-sized content may have slight white margins on the sides due to the narrower A4 width. This is usually acceptable for digital viewing.
- 💡 For print production, normalize all pages to the same size before merging — printers require consistent page dimensions, and mixed-size PDFs cause feed errors on most printers.
- 💡 Merge landscape charts and portrait text by preserving original sizes rather than forcing everything to one orientation — viewers handle mixed orientation naturally.
Privacy & Security
All processing happens directly in your browser. Your files are never uploaded to any server — they remain on your device throughout the entire process. SublimePDF uses WebAssembly technology for fast, secure, client-side processing.
Works Everywhere
This tool works on any modern browser — Chrome, Firefox, Safari, or Edge — on desktop, tablet, or mobile. No software to install. PDF is an open ISO standard supported by all major platforms.
How to Merge PDF With Different Sizes — FAQ
What happens if I merge A4 and Letter PDFs without any options?
Does normalizing page sizes affect image quality?
Can I merge landscape and portrait pages?
How do I ensure consistent margins after merging?
Related Guides
How to Merge PDF Files Online
Merging PDF files is one of the most common PDF tasks — whether you're combining reports, contracts, or scanned pages into a single document. SublimePDF lets you merge PDFs instantly in your browser with no file uploads to any server.
How to Merge PDF On Mac
macOS includes built-in PDF merging through Preview, making it one of the few operating systems where you can combine PDFs without extra software. However, Preview's approach has limitations—it modifies the original file, offers no compression, and doesn't support batch operations. For quick two-file merges, Preview is convenient. For anything more complex, SublimePDF's online tool provides reordering, selective page merging, and file size optimization.
How to Merge PDF On Windows
Windows doesn't include a native PDF merging tool—Microsoft Print to PDF can create PDFs but can't combine them. Most Windows users resort to paid software like Adobe Acrobat or random free tools bundled with adware. SublimePDF's web-based merge tool works in any Windows browser (Edge, Chrome, Firefox) with no installation, no ads, and no file size surprises. For power users, PowerShell and command-line options also exist.