ORIGINAL BROWSER MERGE-INTEGRITY STUDY · 16 SEPTEMBER 2026
Does merging PDFs preserve page order and selectable text?
In PaperGrid's controlled six-page browser test, all eight integrity checks passed: file order, page count, selectable marker text, rotations, page sizes and the custom crop box were preserved, and every output page reopened and rendered.
The merger copied pages from three deterministic synthetic PDFs in selected file order C → A → B. It did not intentionally rasterize or recompress page content. This small test supports those specific results only; forms, digital signatures, embedded files, complex fonts and malformed PDFs were not tested.
C1, C2, C3, A1, A2, B1
Every marker remained selectable
Reopen, geometry and rendering
| Check | Result | How it was verified |
|---|---|---|
| Output reopened | Pass | Loaded again with pdf-lib and PDF.js |
| Page count | 6 of 6 | Both readers reported six pages |
| Selected file order | C → A → B | Extracted labels were C1, C2, C3, A1, A2, B1 |
| Selectable marker text | 6 of 6 | PDF.js extracted the expected label from every page |
| Page rotations | All preserved | Expected 180° and 90° pages remained rotated |
| Page dimensions | 6 of 6 | Portrait, landscape and custom sizes matched exactly |
| Custom crop box | Preserved | x 18, y 24, width 576, height 744 |
| Output rendering | 6 of 6 | PDF.js rendered every page without an error |
METHOD
Exactly how the merge test was run
- Three PDFs were generated deterministically with two, one and three pages. Pages used portrait, landscape and custom dimensions, plus 90° and 180° rotations and one non-default crop box.
- Every page included a unique selectable label such as “SOURCE C PAGE 1.” Source SHA-256 hashes were recorded in the downloadable data.
- The inputs were merged in C → A → B order using the production sequence: load each PDF, copy all its pages, add those pages to one output and save with object streams.
- The output was reopened with pdf-lib to inspect page count, rotation, dimensions and crop boxes. PDF.js independently extracted marker text and rendered all six pages.
- The output SHA-256 hash, exact bytes, processing time, extracted labels, geometry and all pass/fail decisions were recorded.
What this supports
- The selected file and page order survived this run.
- The six tested marker labels remained selectable.
- The tested rotations, page sizes and crop box survived.
- All output pages reopened and rendered.
What it does not prove
- That every PDF feature is preserved.
- That complex fonts render pixel-identically.
- That forms or signatures remain functional or valid.
- That damaged or encrypted PDFs can be merged.
Why output size changed
The output was 2,889 bytes while the three sources totaled 4,490 bytes. This is not presented as compression: rebuilding can deduplicate shared resources and rewrite structure. File size alone does not establish visual quality.
REPRODUCE AND INSPECT
Run the same browser checks
The public lab generates the three safe synthetic sources, runs the production page-copy sequence and displays the measurements in your browser. You can also use Merge PDF's safe sample files without selecting private documents. The downloadable JSON records this study's exact hashes and results.
QUESTIONS & ANSWERS
PDF merge quality FAQ
Does merging PDFs reduce their quality?
PaperGrid copies existing PDF pages into a new document instead of intentionally rasterizing them. In this controlled six-page test, page order, selectable marker text, rotations, page sizes and a custom crop box were preserved. That does not guarantee every advanced PDF feature will survive unchanged.
Does text remain selectable after merging PDFs?
All six deterministic marker labels remained extractable with PDF.js after this merge. The study did not test every font, writing system or complex text encoding.
Are PDF forms and digital signatures preserved when merging?
This benchmark did not test forms, digital signatures, embedded files or portfolios. These features can depend on document-level structures rather than page content, so review the merged output and keep the originals.
Were the benchmark PDFs uploaded?
No. The deterministic fixtures were generated, merged, reopened, text-checked and rendered inside an isolated local browser session.