No: pages are not resized to match when you use Alternate Mix PDF to alternate PDF pages. The tool interleaves two local PDFs in a fixed reading order: A1, B1, A2, B2, and so on, while copying each source page into a new downloadable PDF. It does not impose the first file's size on later pages, stretch content, turn pages into screenshots, or insert blank separator pages. A page with one page-box size from A remains that size, and a differently sized page from B remains its own size. Each page retains its own rotation, vector drawing, text, and embedded raster content to the extent supported by the page-copy operation. If one file has fewer pages, the remaining pages of the longer file are appended in its existing internal order. The output page count is the sum of both input counts, and the result line should show that total. The first selectable file is A and leads the sequence. Processing, page copying, serialization, and download creation happen inside the browser, with no upload to Lizely. Alternate Mix PDF is therefore the right choice when you want a fixed A/B sequence without changing page dimensions. Try the Alternate Mix PDF to do this in your browser.
What happens to page sizes when PDFs alternate
The key distinction is between page order and page dimensions. Alternate Mix PDF selects one page from A and one from B at each shared position, but it does not choose a common canvas for the resulting document. The copied page retains the PDF page box associated with that source page, so a page with a smaller or larger page box can sit beside a page with a different page box.
There is no resizing step between selecting the files and downloading the result. The tool copies the referenced pages into a fresh document rather than converting them to screenshots. It does not stretch vector content, rasterize text, or force a rotation from one file onto another. Text, vector drawing, and embedded raster content are carried over to the extent supported by the library's page-copy operation.
| Page feature | Result after alternating |
|---|---|
| Page-box dimensions | Each source page keeps its own page box. A differently sized page from B does not inherit A's dimensions. |
| Rotation | Each page keeps the rotation it has in its source PDF. |
| Page content | Vector drawing, text, and embedded raster content are copied as PDF content to the extent supported. |
| Separator pages | No blank separator pages are inserted between the two sources. |
This makes mixed page sizes expected, not an error. The output is a new page sequence, not a resized copy. If every page must be standardized to one page format, run that operation separately. The alternation step itself will not enlarge, shrink, stretch, or reformat a page to match another.
Confirm the A/B order before mixing
The order rule is intentionally fixed and visible. The first selectable file is always A. With A selected first, the opening sequence is A1, B1, A2, B2. If you select the same two documents in the opposite order, the sequence is B1, A1, B2, A2. The interface does not infer front versus back scans from filenames or page content, so you retain control over which stream leads.
Confirm that each source PDF is already in the intended internal order. Neither input is reversed automatically. If a scanner produced one stack in reverse, use Reorder PDF Pages before mixing. Alternate Mix PDF does not reverse either input, select ranges, deduplicate pages, or compare content. A filename such as "front" or "back" does not establish the page order for the tool.
| Input pattern | Shared alternating pages | Unmatched tail |
|---|---|---|
| A has 3 pages; B has 2 pages | A1, B1, A2, B2 | A3 is appended in A's existing order. |
| A has 1 page; B has 3 pages | A1, B1 | B2 and B3 are appended in B's existing order. |
The result line reports the page count of each input and the total output count. That total must equal the combined number of pages in the two inputs. The alternation does not add blank pages to make the counts match, so the reported total is also a useful check that every source page was included.
Alternate two PDFs without matching page sizes
- Select PDF A first. Choose a non-empty PDF no larger than 25 MiB. A is the leading file, so make sure its first page belongs at the start of the intended sequence.
- Select PDF B. It must also be non-empty and no larger than 25 MiB. The 25 MiB limit applies separately to each input, not to their combined output.
- Confirm the internal order of both files. Page 1 should be the page you want in the first A or B position. If either source is backwards, reorder it before selecting the mix operation.
- Select Alternate and mix PDFs. The operation creates the fixed A1, B1, A2, B2 sequence. It does not resize pages, change their page boxes, or insert separators.
- Read the result line. Confirm the reported page count for A, the page count for B, and the total output count. The total must equal the sum of both input counts. For unequal files, check that the unmatched pages from the longer PDF were appended in source order.
- Download and inspect the result. Check the first pages, the alternating positions, the unmatched tail, and the page dimensions. Keep the original files until you have verified the downloaded PDF.
The generated filename combines both cleaned source names and adds -alternated.pdf. The original files remain unchanged. If you choose a replacement for either input, the old output is cleared, and a job identifier prevents a slower earlier operation from replacing a result made with newer files.
Choose a different operation when dimensions must change
Alternating and resizing solve different problems. If you want all pages of A followed by all pages of B, use Merge PDF. It combines documents in the chosen order instead of creating an A/B alternation. If every output page must be A4, US Letter, Legal, or a percentage-based size, use Resize PDF. That operation standardizes page dimensions and is separate from Alternate Mix PDF.
- Alternate Mix PDF: Interleaves A1, B1, A2, B2 and appends the longer document's remaining pages.
- Merge PDF: Concatenates PDFs in a chosen order without alternating their pages.
- Resize PDF: Changes every page to a selected page size or scale when mixed dimensions are not desired.
- Reorder PDF Pages: Manually changes a source file's internal order before it is used for mixing.
- Booklet PDF: Creates booklet signatures rather than a simple page-level A/B sequence.
Do not choose alternation merely because one source has more pages. A longer source's tail is preserved, not treated as a reason to resize the shorter source. Conversely, if a common page size matters more than retaining each source page box, standardizing the pages is the appropriate separate workflow. Always inspect the final document after the additional operation, because the last page-size change controls the dimensions of the final file.
Keep originals safe and understand browser limits
Both PDFs are loaded, copied, combined, and saved locally in the browser. No source file is uploaded to Lizely. The operation runs in one browser tab, and both documents can coexist with the newly serialized result while the file is being created. The practical memory cost can therefore exceed the two source file sizes, even though the file-size limit is checked separately for each input. Close other heavy tabs on a memory-constrained device, and keep irreplaceable originals outside the browser workflow.
Each input must be a non-empty PDF no larger than 25 MiB. The limit applies separately to PDF A and PDF B, not to their combined output. Encrypted, damaged, unsupported, oversized, and incorrectly labeled files produce a visible error. Password protection is not bypassed, so a protected file still needs to be handled according to its permissions before it can be used successfully.
The page-copy behavior preserves each page's own page-box dimensions, rotation, vector drawing, text, and embedded raster content to the extent supported by the library's copy operation. It does not promise that forms, bookmarks, outline destinations, scripts, attachments, and cross-document links will retain the same semantics. Inspect important interactive PDFs after mixing rather than assuming those advanced structures survived unchanged.
For mixed page sizes, the important checks are simple: the first page should come from A, the next should come from B, and the shared sequence should continue in that order. When one file is shorter, every remaining page from the longer file should appear afterward in its original order. The page count should still be the sum of both inputs, with no blank separator pages added. These checks let you confirm that the correct stream led and that none of the source pages were resized, skipped, or silently normalized.